Primarily a UX designer, but making prototypes keeps me up to date in my CS roots
Programmers
Q&A for professional programmers interested in conceptual questions about software development
Academia
Q&A for academics and those enrolled in higher education
Mathematics
Q&A for people studying math at any level and professionals in related fields
Server Fault
Q&A for professional system and network administrators
Geographic Information Systems
Q&A for cartographers, geographers and GIS professionals
Cross Validated
Q&A for statisticians, data analysts, data miners and data visualization experts
User Experience
Q&A for user experience researchers and experts
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Graphic Design
Q&A for professional graphic designers and non-designers trying to do their own graphic design
Cognitive Sciences
Q&A for practitioners, researchers, and students in cognitive science, psychology, neuroscience, and psychiatry
Windows Phone
Q&A for enthusiasts and power users of Windows Phone OS
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites