There is so much code waiting to be written...
Stack Overflow
Q&A for professional and enthusiast programmers
Super User
Q&A for computer enthusiasts and power users
Travel
Q&A for road warriors and seasoned travelers
User Experience
Q&A for user experience researchers and experts
Area 51
Q&A for proposing new sites in the Stack Exchange network
Physics
Q&A for active researchers, academics and students of physics
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Puzzling
Q&A for those who create, solve, and study puzzles
Information Security
Q&A for information security professionals
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Hardware Recommendations
Q&A for people seeking specific hardware recommendations
Worldbuilding
Q&A for writers/artists using science, geography and culture to construct imaginary worlds and settings
Skeptics
Q&A for scientific skepticism
Open Source
Q&A for people organizing, marketing or licensing open source development projects
Network Engineering
Q&A for network engineers
MathOverflow
Q&A for professional mathematicians
Academia
Q&A for academics and those enrolled in higher education
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
Parenting
Q&A for parents, grandparents, nannies and others with a parenting role
Game Development
Q&A for professional and independent game developers
The Workplace
Q&A for members of the workforce navigating the professional setting
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Server Fault
Q&A for system and network administrators
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Ask Ubuntu
Q&A for Ubuntu users and developers
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Role-playing Games
Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
Arqade
Q&A for passionate videogamers on all platforms
Mathematics
Q&A for people studying math at any level and professionals in related fields
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites