Mathematics
Q&A for people studying math at any level and professionals in related fields
Stack Overflow
Q&A for professional and enthusiast programmers
Physics
Q&A for active researchers, academics and students of physics
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
History of Science and Mathematics
Q&A for people interested in the history and origins of science and mathematics
Blender
Q&A for people who use Blender to create 3D graphics, animations, or games
Aviation
Q&A for aircraft pilots, mechanics, and enthusiasts
MathOverflow
Q&A for professional mathematicians
Signal Processing
Q&A for practitioners of the art and science of signal, image and video processing
Game Development
Q&A for professional and independent game developers
Engineering
Q&A for professionals and students of engineering
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems
Super User
Q&A for computer enthusiasts and power users
Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Electrical Engineering
Q&A for electronics and electrical engineering professionals, students, and enthusiasts