Stack Overflow
Q&A for professional and enthusiast programmers
Japanese Language
Q&A for students, teachers, and linguists wanting to discuss the finer points of the Japanese language
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Super User
Q&A for computer enthusiasts and power users
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Server Fault
Q&A for system and network administrators
Emacs
Q&A for those using, extending or developing Emacs
Information Security
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Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Mathematics
Q&A for people studying math at any level and professionals in related fields
Ask Different
Q&A for power users of Apple hardware and software
English Language & Usage
Q&A for linguists, etymologists, and serious English language 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
English Language Learners
Q&A for speakers of other languages learning English
Database Administrators
Q&A for database professionals who wish to improve their database skills and learn from others in the community
Arqade
Q&A for passionate videogamers on all platforms
Retrocomputing
Q&A for vintage-computer hobbyists interested in restoring, preserving, and using the classic computer and gaming systems of yesteryear