Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems.
Personal Productivity
Q&A for people wanting to improve their personal productivity
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
The Great Outdoors
Q&A for people who love outdoor activities, excursions, and outdoorsmanship
Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Programmers
Q&A for professional programmers interested in conceptual questions about software development
Server Fault
Q&A for professional system and network administrators
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Physical Fitness
Q&A for physical fitness professionals, athletes, trainers, and those providing health-related needs