Stack Overflow
Q&A for professional and enthusiast programmers
Mathematics
Q&A for people studying math at any level and professionals in related fields
Physics
Q&A for active researchers, academics and students of physics
Ask Different
Q&A for power users of Apple hardware and software
Photography
Q&A for professional, enthusiast and amateur photographers
WordPress Answers
Q&A for WordPress developers and administrators
Programmers
Q&A for professional programmers interested in conceptual questions about software development
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
User Experience
Q&A for user experience researchers and experts
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Server Fault
Q&A for professional system and network administrators
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Stack Apps
Q&A for apps, scripts, and development with the Stack Exchange API
Cross Validated
Q&A for statisticians, data analysts, data miners and data visualization experts
Software Quality Assurance & Testing
Q&A for software quality control experts, automation engineers, and software testers
German Language & Usage
Q&A for speakers of German wanting to discuss the finer points of the language and translation
Robotics
Q&A for professional robotic engineers, hobbyists, researchers and students
Computer Science
Q&A for students, researchers and practitioners of computer science
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites