Stack Overflow
Q&A for professional and enthusiast programmers
Signal Processing
Q&A for practitioners of the art and science of signal, image and video processing
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Data Science
Q&A for Data science professionals, Machine Learning specialists, and those interested in learning more about the field
Super User
Q&A for computer enthusiasts and power users
English Language & Usage
Q&A for linguists, etymologists, and serious English language enthusiasts
Mathematics
Q&A for people studying math at any level and professionals in related fields
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