Stack Overflow
Q&A for professional and enthusiast programmers
Programmers
Q&A for professional programmers interested in conceptual questions about software development
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
Game Development
Q&A for professional and independent game developers
Graphic Design
Q&A for professional graphic designers and non-designers trying to do their own graphic design
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Cross Validated
Q&A for statisticians, data analysts, data miners and data visualization experts
Ask Different
Q&A for power users of Apple hardware and software
Stack Apps
Q&A for apps, scripts, and development with the Stack Exchange API
Photography
Q&A for professional, enthusiast and amateur photographers
Server Fault
Q&A for professional system and network administrators
User Experience
Q&A for user experience researchers and experts
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
Answers OnStartups
Q&A for entrepreneurs looking to start or run a new business