Bicycles
Q&A for people who build and repair bicycles, people who train cycling, or commute on bicycles
Portuguese Language
Q&A for linguists, teachers and learners wanting to discuss the finer points of the Portuguese language
Ask Ubuntu
Q&A for Ubuntu users and developers
Information Security
Q&A for information security professionals
Emacs
Q&A for those using, extending or developing Emacs
Super User
Q&A for computer enthusiasts and power users
Stack Overflow
Q&A for professional and enthusiast programmers
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Engineering
Q&A for professionals and students of engineering
Vi and Vim
Q&A for people using the vi and Vim families of text editors
Language Learning
Q&A for students, teachers, polyglots, and anyone interested in the techniques of second-language acquisition
Meta Stack Exchange
Q&A for meta-discussion of the Stack Exchange family of Q&A websites
Open Data
Q&A for developers and researchers interested in open data
TeX - LaTeX
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems