- The Not So Short Introduction to LaTeX 2ε—a very nice introductory book
- Formatting information. A beginner's introduction to typesetting with LaTeX—another introduction (also in pdf format)
- An essential guide to LaTeX2e usage. Obsolete commands and packages—a booklet useful especially for people moving from LaTeX 2.09 to LaTeX2e.
- Short Math Guide for LaTeX, aimed especially for mathematicians
- A wikibook on LaTeX (not the best source, but may be useful)
- The Comprehensive LaTeX Symbol List (letter format)
- Scott Pakin's The Visual LaTeX FAQ

- TeX Users Group homepage
- TeX.SE -- a great Q&A site and community
- UK List of TeX Frequently Asked Questions
- Comprehensive TeX Archive Network (CTAN)
- TeXample—a TeX blog aggregator and lots of examples of graphics in LaTeX

…and others will follow.