Server Fault
Q&A for professional system and network administrators
Programmers
Q&A for professional programmers interested in conceptual questions about software development
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
Web Applications
Q&A for power users of web applications
Physics
Q&A for active researchers, academics and students of physics
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
User Experience
Q&A for user experience researchers and experts
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Photography
Q&A for professional, enthusiast and amateur photographers
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Ask Different
Q&A for power users of Apple hardware and software
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
Drupal Answers
Q&A for Drupal developers and administrators
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems.
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Stack Apps
Q&A for apps, scripts, and development with the Stack Exchange API
Game Development
Q&A for professional and independent game developers
Mathematics
Q&A for people studying math at any level and professionals in related fields
Writers
Q&A for authors, editors, reviewers, professional writers, and aspiring writers
Reverse Engineering
Q&A for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation
English Language Learners
Q&A for speakers of other languages learning English
Programming Puzzles & Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Software Quality Assurance & Testing
Q&A for software quality control experts, automation engineers, and software testers
Parenting
Q&A for parents, grandparents, nannies and others with a parenting role
Personal Productivity
Q&A for people wanting to improve their personal productivity
Personal Finance & Money
Q&A for people who want to be financially literate
The Workplace
Q&A for members of the workforce navigating the professional setting
Ask Patents
Q&A for people interested in improving and participating in the patent system