There will be more to say here - once I remember all the interesting details that make me worth your time to read.
Stack Overflow
Q&A for professional and enthusiast programmers
Super User
Q&A for computer enthusiasts and power users
Web Applications
Q&A for power users of web applications
Graphic Design
Q&A for Graphic Design professionals, students, and enthusiasts
Game Development
Q&A for professional and independent game developers
Mathematics
Q&A for people studying math at any level and professionals in related fields
Operations Research
Q&A for operations research and analytics professionals, educators, and students
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Writing
Q&A for the craft of professional writing, including fiction, non-fiction, technical, scholarly, and commercial writing
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Chemistry
Q&A for scientists, academics, teachers, and students in the field of chemistry
Geographic Information Systems
Q&A for cartographers, geographers and GIS professionals