The Lion 

TeX user groups

DK-TUG (Danish TeX Users Group)
TUG (TeX Users Group)
TeX Users Group Worldwide

FAQs, books, tutorials

Sources and resources

On the strength and weakness of TeX
(from http://www.topology.org/soft/tex.html by Allan Kennington)

 TeX is the venerable and still revolutionary typesetting software from Donald Knuth. My documents written in TeX
 in 1985 still work exactly the same now as then. And TeX is still by far the best typesetting system. No versionitis.
 No bugs. And it's free and open. TeX is what started the open source revolution, not Richard Stallman's FSF.

and

TeX has caused me to weep with frustration far more often than any other piece of software. The full use of TeX
requires an IQ in excess of 150. The plain TeX textbook is one of the most incomprehensible user manuals
ever written. The TeX language is one of the worst-designed and incomprehensible languages ever invented.If there were any software that could achieve similar results with less pain, I would use it. One can only pray that some day someone will write a comprehensive rationally thought-out front end for TeX and a user manual that assumes an IQ less than 200. (Since gods are all in the mind, praying has no hope of success, but it does relieve the pain a little.)