Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Stack Overflow
Q&A for professional and enthusiast programmers
Ask Ubuntu
Q&A for Ubuntu users and developers
Super User
Q&A for computer enthusiasts and power users
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
English Language Learners
Q&A for speakers of other languages learning English
Vi and Vim
Q&A for people using the vi and Vim families of text editors
Ask Different
Q&A for power users of Apple hardware and software
Code Review
Q&A for peer programmer code reviews
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Mathematics
Q&A for people studying math at any level and professionals in related fields
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
User Experience
Q&A for user experience researchers and experts
Server Fault
Q&A for system and network administrators
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Literature
Q&A for scholars and enthusiasts of literature
The Workplace
Q&A for members of the workforce navigating the professional setting
Arqade
Q&A for passionate videogamers on all platforms
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings