Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Stack Overflow
Q&A for professional and enthusiast programmers
Super User
Q&A for computer enthusiasts and power users
Vi and Vim
Q&A for people using the vi and Vim families of text editors
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Politics
Q&A for people interested in governments, policies, and political processes
Physics
Q&A for active researchers, academics and students of physics
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Android Enthusiasts
Q&A for enthusiasts and power users of the Android operating system
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
Artificial Intelligence
Q&A for people interested in conceptual questions about life and challenges in a world where "cognitive" functions can be mimicked in purely digital environment
Quantitative Finance
Q&A for finance professionals and academics
Mathematics
Q&A for people studying math at any level and professionals in related fields
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Server Fault
Q&A for system and network administrators
Personal Finance & Money
Q&A for people who want to be financially literate
Raspberry Pi
Q&A for users and developers of hardware and software for Raspberry Pi
Information Security
Q&A for information security professionals
Gardening & Landscaping
Q&A for gardeners and landscapers