Puzzling
Q&A for those who create, solve, and study puzzles
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Physics
Q&A for active researchers, academics and students of physics
Stack Overflow
Q&A for professional and enthusiast programmers
Mathematics
Q&A for people studying math at any level and professionals in related fields
Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
MathOverflow
Q&A for professional mathematicians
Graphic Design
Q&A for Graphic Design professionals, students, and enthusiasts
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Movies & TV
Q&A for movie and TV enthusiasts
Blender
Q&A for people who use Blender to create 3D graphics, animations, or games
Board & Card Games
Q&A for people who like playing board games, designing board games or modifying the rules of existing board games
Photography
Q&A for professional, enthusiast and amateur photographers
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system