Stack Overflow
Q&A for professional and enthusiast programmers
Ask Ubuntu
Q&A for Ubuntu users and developers
Photography
Q&A for professional, enthusiast and amateur photographers
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Ask Different
Q&A for power users of Apple hardware and software
Graphic Design
Q&A for Graphic Design professionals, students, and enthusiasts
Emacs
Q&A for those using, extending or developing Emacs
Server Fault
Q&A for system and network administrators
Home Improvement
Q&A for contractors and serious DIYers
Vi and Vim
Q&A for people using the vi and Vim families of text editors
Web Applications
Q&A for power users of web applications
Information Security
Q&A for information security professionals
Ask Patents
Q&A for people interested in improving the patent system
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts