Philosophy
Q&A for those interested in the study of the fundamental nature of knowledge, reality, and existence
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Physics
Q&A for active researchers, academics and students of physics
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
Puzzling
Q&A for those who create, solve, and study puzzles
Mathematics
Q&A for people studying math at any level and professionals in related fields
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Mathematics Educators
Q&A for those involved in the field of teaching mathematics
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
Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Economics
Q&A for those who study, teach, research and apply economics and econometrics
Cryptography
Q&A for software developers, mathematicians and others interested in cryptography
Politics
Q&A for people interested in governments, policies, and political processes
Computer Science
Q&A for students, researchers and practitioners of computer science
Buddhism
Q&A for people practicing or interested in Buddhist philosophy, teaching, and practice
Literature
Q&A for scholars and enthusiasts of literature
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
Writing
Q&A for the craft of professional writing, including fiction, non-fiction, technical, scholarly, and commercial writing
English Language Learners
Q&A for speakers of other languages learning English
Academia
Q&A for academics and those enrolled in higher education
MathOverflow
Q&A for professional mathematicians
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
Stack Overflow
Q&A for professional and enthusiast programmers
History of Science and Mathematics
Q&A for people interested in the history and origins of science and mathematics
Space Exploration
Q&A for spacecraft operators, scientists, engineers, and enthusiasts
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Computational Science
Q&A for scientists using computers to solve scientific problems
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Biology
Q&A for biology researchers, academics, and students
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts