Stack Overflow
Q&A for professional and enthusiast programmers
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Emacs
Q&A for those using, extending or developing Emacs
Super User
Q&A for computer enthusiasts and power users
Geographic Information Systems
Q&A for cartographers, geographers and GIS professionals
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Japanese Language
Q&A for students, teachers, and linguists wanting to discuss the finer points of the Japanese language
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Writing
Q&A for the craft of professional writing, including fiction, non-fiction, technical, scholarly, and commercial writing
Web Applications
Q&A for power users of web applications
Server Fault
Q&A for system and network administrators
Seasoned Advice
Q&A for professional and amateur chefs
Retrocomputing
Q&A for vintage-computer hobbyists interested in restoring, preserving, and using the classic computer and gaming systems of yesteryear
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Vi and Vim
Q&A for people using the vi and Vim families of text editors
Music: Practice & Theory
Q&A for musicians, students, and enthusiasts
Interpersonal Skills
Q&A for people looking to improve their interpersonal communication skills