Stack Overflow
Q&A for professional and enthusiast programmers
Code Review
Q&A for peer programmer code reviews
Mathematics
Q&A for people studying math at any level and professionals in related fields
Engineering
Q&A for professionals and students of engineering
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Space Exploration
Q&A for spacecraft operators, scientists, engineers, and enthusiasts
Super User
Q&A for computer enthusiasts and power users
Physics
Q&A for active researchers, academics and students of physics
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
History of Science and Mathematics
Q&A for people interested in the history and origins of science and mathematics
Arduino
Q&A for developers of open-source hardware and software that is compatible with Arduino
Computational Science
Q&A for scientists using computers to solve scientific problems
Server Fault
Q&A for system and network administrators
Ask Different
Q&A for power users of Apple hardware and software
Raspberry Pi
Q&A for users and developers of hardware and software for Raspberry Pi
Martial Arts
Q&A for students and teachers of all martial arts
Artificial Intelligence
Q&A for people interested in conceptual questions about life and challenges in a world where "cognitive" functions can be mimicked in purely digital environment
Skeptics
Q&A for scientific skepticism
Computer Science
Q&A for students, researchers and practitioners of computer science
Quantitative Finance
Q&A for finance professionals and academics
Academia
Q&A for academics and those enrolled in higher education
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Law
Q&A for legal professionals, students, and others with experience or interest in law