Stack Overflow
Q&A for professional and enthusiast programmers
Ask Ubuntu
Q&A for Ubuntu users and developers
Blender
Q&A for people who use Blender to create 3D graphics, animations, or games
Poker
Q&A for serious players and enthusiasts of poker
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Server Fault
Q&A for system and network administrators
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Emacs
Q&A for those using, extending or developing Emacs
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Ask Different
Q&A for power users of Apple hardware and software
Network Engineering
Q&A for network engineers
Game Development
Q&A for professional and independent game developers
Super User
Q&A for computer enthusiasts and power users
User Experience
Q&A for user experience researchers and experts
Vi and Vim
Q&A for people using the vi and Vim families of text editors