Super User
Q&A for computer enthusiasts and power users
Stack Overflow
Q&A for professional and enthusiast programmers
Robotics
Q&A for professional robotic engineers, hobbyists, researchers and students
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Server Fault
Q&A for system and network administrators
Photography
Q&A for professional, enthusiast and amateur photographers
Space Exploration
Q&A for spacecraft operators, scientists, engineers, and enthusiasts
The Great Outdoors
Q&A for people who love being outdoors enjoying nature and wilderness, and learning about the required skills and equipment
Mathematics
Q&A for people studying math at any level and professionals in related fields
Information Security
Q&A for information security professionals
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Science Fiction & Fantasy
Q&A for science fiction and fantasy enthusiasts
Anime & Manga
Q&A for anime and manga fans
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems