Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Stack Overflow
Q&A for professional and enthusiast programmers
Christianity
Q&A for committed Christians, experts in Christianity and those interested in learning more
Super User
Q&A for computer enthusiasts and power users
Physics
Q&A for active researchers, academics and students of physics
Islam
Q&A for Muslims, experts in Islam, and those interested in learning more about Islam
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Mi Yodeya
Q&A for those who base their lives on Jewish law and tradition and anyone interested in learning more
Area 51
Q&A for proposing new sites in the Stack Exchange network
Astronomy
Q&A for astronomers and astrophysicists
Web Applications
Q&A for power users of web applications
Biology
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User Experience
Q&A for user experience researchers and experts
WordPress Development
Q&A for WordPress developers and administrators
Theoretical Computer Science
Q&A for theoretical computer scientists and researchers in related fields
Philosophy
Q&A for those interested in the study of the fundamental nature of knowledge, reality, and existence
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Code Review
Q&A for peer programmer code reviews
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts