BookofZeus.com: The web resource for articles for the open source community. Book Of Zeus is a website dedicated to learning and teaching open source technology such as PHP, MySQL and Linux.
Stack Overflow
Q&A for professional and enthusiast programmers
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
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
Stack Apps
Q&A for apps, scripts, and development with the Stack Exchange API
Ask Different
Q&A for power users of Apple hardware and software
Programmers
Q&A for professional programmers interested in conceptual questions about software development
