I mostly live in the Sci-Fi, Gaming & Cartoon world, but -- at night -- I secretly masquerade as someone who pretends to know Arduino, Linux, Java & jQuery.
Disclaimer: I have no idea what I'm talking about, all my answers are guesses!
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Physics
Q&A for active researchers, academics and students of physics
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Answers OnStartups
Q&A for entrepreneurs looking to start or run a new business
Drupal Answers
Q&A for Drupal developers and administrators
Stack Overflow
Q&A for professional and enthusiast programmers
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
WordPress Answers
Q&A for WordPress developers and administrators
Server Fault
Q&A for professional system and network administrators
Mathematics
Q&A for people studying math at any level and professionals in related fields
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Game Development
Q&A for professional and independent game developers
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems.
Programmers
Q&A for professional programmers interested in conceptual questions about software development
