Stack Overflow
Q&A for professional and enthusiast programmers
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
Server Fault
Q&A for professional system and network administrators
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Programmers
Q&A for professional programmers interested in conceptual questions about software development
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
Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Cryptography
Q&A for software developers, mathematicians and others interested in cryptography
Quantitative Finance
Q&A for finance professionals and academics
Biology
Q&A for biology researchers, academics, and students
