Signal Processing
Q&A for practitioners of the art and science of signal, image and video processing
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Cross Validated
Q&A for statisticians, data analysts, data miners and data visualization experts
Biology
Q&A for biology researchers, academics, and students
Programmers
Q&A for professional programmers interested in conceptual questions about software development
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
French Language & Usage
Q&A for students, teachers, and linguists wanting to discuss the finer points of the French language
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
German Language & Usage
Q&A for speakers of German wanting to discuss the finer points of the language and translation
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
Programming Puzzles & Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Mathematics
Q&A for people studying math at any level and professionals in related fields
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems.
Ask Different
Q&A for power users of Apple hardware and software
User Experience
Q&A for user experience researchers and experts
Physics
Q&A for active researchers, academics and students of physics
Stack Apps
Q&A for apps, scripts, and development with the Stack Exchange API
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Server Fault
Q&A for professional system and network administrators
Parenting
Q&A for parents, grandparents, nannies and others with a parenting role
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games