Web Forums:

• TeX, LaTeX and friends on Stack Exchange
• LaTeX Community
  LaTeX-dedicated web forum: discussions about LaTeX, Distributions, Editors
• CQF.info now dead
  LaTeX subforum of the CQF board
• Art of Problem Solving
  (LaTeX subforum)
• mrunix.de
  LaTeX subforum of the mrunix board, well frequented
• Textsatz mit LaTeX
  subforum of matheplanet.com, a big German math site
• LaTeX on Apfeltalk
  subforum of the German apple mac forum dedicated to LaTeX discussions, helpful for mac users
• Chemie online
  LaTeX subforum of chemistry discussion board
• MatheBoard
  subforum of the math board
• Mathe-Raum
  subforum of the Mathe-Raum math board
• goLaTeX
  German LaTeX forum, online since June 08
• Dutch LaTeX Forum

Usenet groups:

• comp.text.tex
  usenet discussion group for TeX and LaTeX
• de.comp.text.tex
  German usenet discussion group for TeX and LaTeX