Cryptography
Q&A for software developers, mathematicians and others interested in cryptography
Area 51
Stack Exchange Network staging zone, where users come together to build new Q&A sites
Programming Puzzles & Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Cross Validated
Q&A for statisticians, data analysts, data miners and data visualization experts
Physics
Q&A for active researchers, academics and students of physics
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
Game Development
Q&A for professional and independent game developers
Meta Stack Overflow
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
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.
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Software Quality Assurance & Testing
Q&A for software quality control experts, automation engineers, and software testers