I was one of the Drupal core maintainers. I was also one of the senior programmers / architects of a Top 100 website built on top of Drupal 7 and MongoDB. These days I work on Drupal 8, making it compatible with MongoDB and creating a migrate path from Drupal 6 and 7.
Stack Overflow
Q&A for professional and enthusiast programmers
Mathematics
Q&A for people studying math at any level and professionals in related fields
Server Fault
Q&A for system and network administrators
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
Retrocomputing
Q&A for vintage-computer hobbyists interested in restoring, preserving, and using the classic computer and gaming systems of yesteryear
Drupal Answers
Q&A for Drupal developers and administrators
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Expatriates
Q&A for people living abroad on a long-term basis
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Ask Ubuntu
Q&A for Ubuntu users and developers
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
Personal Finance & Money
Q&A for people who want to be financially literate
Information Security
Q&A for information security professionals
Ask Different
Q&A for power users of Apple hardware and software
Arqade
Q&A for passionate videogamers on all platforms
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Hardware Recommendations
Q&A for people seeking specific hardware recommendations
Web Applications
Q&A for power users of web applications
Law
Q&A for legal professionals, students, and others with experience or interest in law
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Software Recommendations
Q&A for people seeking specific software recommendations
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Politics
Q&A for people interested in governments, policies, and political processes
Linguistics
Q&A for professional linguists and others with an interest in linguistic research and theory
Home Improvement
Q&A for contractors and serious DIYers
Academia
Q&A for academics and those enrolled in higher education
Mathematics Educators
Q&A for those involved in the field of teaching mathematics
Computer Science
Q&A for students, researchers and practitioners of computer science
English Language Learners
Q&A for speakers of other languages learning English
Game Development
Q&A for professional and independent game developers
Area 51
Q&A for proposing new sites in the Stack Exchange network
Physics
Q&A for active researchers, academics and students of physics
Puzzling
Q&A for those who create, solve, and study puzzles
Engineering
Q&A for professionals and students of engineering
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Network Engineering
Q&A for network engineers
Parenting
Q&A for parents, grandparents, nannies and others with a parenting role
Chess
Q&A for serious players and enthusiasts of chess
Biblical Hermeneutics
Q&A for professors, theologians, and those interested in exegetical analysis of biblical texts
Writing
Q&A for the craft of professional writing, including fiction, non-fiction, technical, scholarly, and commercial writing
Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
Graphic Design
Q&A for Graphic Design professionals, students, and enthusiasts
Economics
Q&A for those who study, teach, research and apply economics and econometrics
Salesforce
Q&A for Salesforce administrators, implementation experts, developers and anybody in-between
Arduino
Q&A for developers of open-source hardware and software that is compatible with Arduino
Anime & Manga
Q&A for anime and manga fans
Video Production
Q&A for engineers, producers, editors and enthusiasts spanning the fields of video and media creation
Literature
Q&A for scholars and enthusiasts of literature
Reverse Engineering
Q&A for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation
Earth Science
Q&A for those interested in the geology, meteorology, oceanography, and environmental sciences
Motor Vehicle Maintenance & Repair
Q&A for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles
Computer Science Educators
Q&A for those involved in the field of teaching Computer Science
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Raspberry Pi
Q&A for users and developers of hardware and software for Raspberry Pi
Computational Science
Q&A for scientists using computers to solve scientific problems
Ebooks
Q&A for ebook publishers and readers
The Great Outdoors
Q&A for people who love being outdoors enjoying nature and wilderness, and learning about the required skills and equipment
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Music: Practice & Theory
Q&A for musicians, students, and enthusiasts
Photography
Q&A for professional, enthusiast and amateur photographers
Pets
Q&A for pet owners, caretakers, breeders, veterinarians, and trainers
The Workplace
Q&A for members of the workforce navigating the professional setting
MathOverflow
Q&A for professional mathematicians
Lifehacks
Q&A for people looking to bypass life's everyday problems with simple tricks
Philosophy
Q&A for those interested in the study of the fundamental nature of knowledge, reality, and existence
User Experience
Q&A for user experience researchers and experts
Cryptography
Q&A for software developers, mathematicians and others interested in cryptography
Monero
Q&A for developers and users of the secure, private and untraceable cryptocurrency Monero
Seasoned Advice
Q&A for professional and amateur chefs
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
WordPress Development
Q&A for WordPress developers and administrators
Bitcoin
Q&A for Bitcoin users, developers, and enthusiasts
Mi Yodeya
Q&A for those who base their lives on Jewish law and tradition and anyone interested in learning more
Interpersonal Skills
Q&A for people looking to improve their interpersonal communication skills
Ask Patents
Q&A for people interested in improving the patent system
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
Ethereum
Q&A for users of Ethereum, the decentralized application platform and smart contract enabled blockchain