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
Photography
Q&A for professional, enthusiast and amateur photographers
Ask Patents
Q&A for people interested in improving and participating in the patent system
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Server Fault
Q&A for professional system and network administrators
Physics
Q&A for active researchers, academics and students of physics
Mi Yodeya
Q&A for those who base their lives on Jewish law and tradition and anyone interested in learning more
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
Ask Different
Q&A for power users of Apple hardware and software
Mathematics
Q&A for people studying math at any level and professionals in related fields
User Experience
Q&A for user experience researchers and experts
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Programming Puzzles & Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Chemistry
Q&A for scientists, academics, teachers and students
Quantitative Finance
Q&A for finance professionals and academics
Computer Science
Q&A for students, researchers and practitioners of computer science
Parenting
Q&A for parents, grandparents, nannies and others with a parenting role