TeX user since 1989, mostly LaTeX. For some time maintainer of pdfTeX, since then a close friend of the LuaTeX team.
Text building blocks
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Ask Ubuntu
Q&A for Ubuntu users and developers
Stack Overflow
Q&A for professional and enthusiast programmers
Politics
Q&A for people interested in governments, policies, and political processes
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Space Exploration
Q&A for spacecraft operators, scientists, engineers, and enthusiasts
History
Q&A for historians and history buffs
Skeptics
Q&A for scientific skepticism
Arqade
Q&A for passionate videogamers on all platforms
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
Physics
Q&A for active researchers, academics and students of physics
Code Review
Q&A for peer programmer code reviews
Movies & TV
Q&A for movie and TV enthusiasts
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Ebooks
Q&A for ebook publishers and readers
Super User
Q&A for computer enthusiasts and power users
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Server Fault
Q&A for system and network administrators
Pets
Q&A for pet owners, caretakers, breeders, veterinarians, and trainers
Open Source
Q&A for people organizing, marketing or licensing open source development projects
Information Security
Q&A for information security professionals
Law
Q&A for legal professionals, students, and others with experience or interest in law
Sports
Q&A for participants in team and individual sport activities
Travel
Q&A for road warriors and seasoned travelers
Academia
Q&A for academics and those enrolled in higher education
Software Recommendations
Q&A for people seeking specific software recommendations
Retrocomputing
Q&A for vintage-computer hobbyists interested in restoring, preserving, and using the classic computer and gaming systems of yesteryear
Web Applications
Q&A for power users of web applications
Graphic Design
Q&A for Graphic Design professionals, students, and enthusiasts
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Area 51
Q&A for proposing new sites in the Stack Exchange network
Astronomy
Q&A for astronomers and astrophysicists
Biology
Q&A for biology researchers, academics, and students
Network Engineering
Q&A for network engineers
Anime & Manga
Q&A for anime and manga fans
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
The Workplace
Q&A for members of the workforce navigating the professional setting
History of Science and Mathematics
Q&A for people interested in the history and origins of science and mathematics
DevOps
Q&A for software engineers working on automated testing, continuous delivery, service integration and monitoring, and building SDLC infrastructure
Literature
Q&A for scholars and enthusiasts of literature
Seasoned Advice
Q&A for professional and amateur chefs
Ask Different
Q&A for power users of Apple hardware and software
Personal Finance & Money
Q&A for people who want to be financially literate
Hardware Recommendations
Q&A for people seeking specific hardware recommendations
Ask Patents
Q&A for people interested in improving the patent system
User Experience
Q&A for user experience researchers and experts
Cryptography
Q&A for software developers, mathematicians and others interested in cryptography
Beer, Wine & Spirits
Q&A for alcoholic beverage aficionados and those interested in beer, wine, or spirits
Music Fans
Q&A for music historians, critics, and fans
Home Improvement
Q&A for contractors and serious DIYers
Raspberry Pi
Q&A for users and developers of hardware and software for Raspberry Pi
Writing
Q&A for the craft of professional writing, including fiction, non-fiction, technical, scholarly, and commercial writing
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
German Language
Q&A for speakers of German wanting to discuss the finer points of the language and translation
Coffee
Q&A for people interested in all aspects of producing and consuming coffee
Parenting
Q&A for parents, grandparents, nannies and others with a parenting role
Chemistry
Q&A for scientists, academics, teachers, and students in the field of chemistry
Software Quality Assurance & Testing
Q&A for software quality control experts, automation engineers, and software testers
Interpersonal Skills
Q&A for people looking to improve their interpersonal communication skills
Earth Science
Q&A for those interested in the geology, meteorology, oceanography, and environmental sciences
MathOverflow
Q&A for professional mathematicians
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Arduino
Q&A for developers of open-source hardware and software that is compatible with Arduino
Geographic Information Systems
Q&A for cartographers, geographers and GIS professionals
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
The Great Outdoors
Q&A for people who love being outdoors enjoying nature and wilderness, and learning about the required skills and equipment
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
Music: Practice & Theory
Q&A for musicians, students, and enthusiasts
SharePoint
Q&A for SharePoint enthusiasts
Chess
Q&A for serious players and enthusiasts of chess
Philosophy
Q&A for those interested in the study of the fundamental nature of knowledge, reality, and existence
French Language
Q&A for students, teachers, and linguists wanting to discuss the finer points of the French language
Genealogy & Family History
Q&A for expert genealogists and people interested in genealogy or family history
Sustainable Living
Q&A for folks dedicated to a lifestyle that can be maintained indefinitely without depleting available resources
Martial Arts
Q&A for students and teachers of all martial arts
Japanese Language
Q&A for students, teachers, and linguists wanting to discuss the finer points of the Japanese language
Bioinformatics
Q&A for researchers, developers, students, teachers, and end users interested in bioinformatics
Computer Graphics
Q&A for computer graphics researchers and programmers
Drones and Model Aircraft
Q&A for experienced flyers, pilots, and builders of drones and model aircraft
Amateur Radio
Q&A for amateur radio enthusiasts
Russian Language
Q&A for students, teachers, and linguists wanting to discuss the finer points of the Russian language
Blender
Q&A for people who use Blender to create 3D graphics, animations, or games
Quantum Computing
Q&A for engineers, scientists, programmers, and computing professionals interested in quantum computing
Stack Apps
Q&A for apps, scripts, and development with the Stack Exchange API
Esperanto Language
Q&A for teachers and students of the Esperanto language
Internet of Things
Q&A for builders and users of networked sensors and control devices in the contexts of smart homes, industry automation, or environmental sensors
Ethereum
Q&A for users of Ethereum, the decentralized application platform and smart contract enabled blockchain
Puzzling
Q&A for those who create, solve, and study puzzles
Latin Language
Q&A for linguists, teachers, and students wanting to discuss the finer points of the Latin language
Bitcoin
Q&A for Bitcoin users, developers, and enthusiasts
Salesforce
Q&A for Salesforce administrators, implementation experts, developers and anybody in-between
Christianity
Q&A for committed Christians, experts in Christianity and those interested in learning more
Computer Science Educators
Q&A for those involved in the field of teaching Computer Science
Buddhism
Q&A for people practicing or interested in Buddhist philosophy, teaching, and practice
Freelancing
Q&A for self-employed and freelance workers
Signal Processing
Q&A for practitioners of the art and science of signal, image and video processing
Mathematica
Q&A for users of Wolfram Mathematica
Bricks
Q&A for LEGO® and building block enthusiasts
Psychology & Neuroscience
Q&A for practitioners, researchers, and students in cognitive science, psychology, neuroscience, and psychiatry
Tor
Q&A for researchers, developers, and users of Tor
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Reverse Engineering
Q&A for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation
Photography
Q&A for professional, enthusiast and amateur photographers
Computational Science
Q&A for scientists using computers to solve scientific problems
Video Production
Q&A for engineers, producers, editors and enthusiasts spanning the fields of video and media creation
WordPress Development
Q&A for WordPress developers and administrators
Mi Yodeya
Q&A for those who base their lives on Jewish law and tradition and anyone interested in learning more
Game Development
Q&A for professional and independent game developers
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Linguistics
Q&A for professional linguists and others with an interest in linguistic research and theory
Computer Science
Q&A for students, researchers and practitioners of computer science
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Quantitative Finance
Q&A for finance professionals and academics
Woodworking
Q&A for professional and amateur woodworkers
Matter Modeling
Q&A for materials modelers and data scientists
Mathematics
Q&A for people studying math at any level and professionals in related fields
Mythology & Folklore
Q&A for enthusiasts and scholars of mythology and folklore
Biblical Hermeneutics
Q&A for professors, theologians, and those interested in exegetical analysis of biblical texts
Economics
Q&A for those who study, teach, research and apply economics and econometrics
Engineering
Q&A for professionals and students of engineering
Vi and Vim
Q&A for people using the vi and Vim families of text editors
Gardening & Landscaping
Q&A for gardeners and landscapers
Lifehacks
Q&A for people looking to bypass life's everyday problems with simple tricks
Emacs
Q&A for those using, extending or developing Emacs
Stack Overflow em Português
Perguntas e respostas para programadores profissionais e entusiastas
Motor Vehicle Maintenance & Repair
Q&A for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles
Physical Fitness
Q&A for physical fitness professionals, athletes, trainers, and those providing health-related needs
English Language Learners
Q&A for speakers of other languages learning English
Expatriates
Q&A for people living abroad on a long-term basis
Mathematics Educators
Q&A for those involved in the field of teaching mathematics
Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Sound Design
Q&A for sound engineers, producers, editors, and enthusiasts
Islam
Q&A for Muslims, experts in Islam, and those interested in learning more about Islam
Medical Sciences
Q&A for professionals in medical and allied health fields, students of those professions, related academics, and others with a sound understanding of medicine and healthcare-related sciences
Community Building
Q&A for community managers, administrators, and moderators
Constructed Languages
Q&A for designers and users of artificial or invented languages, consciously developed instead of having developed naturally