LaTeX links

Books, tutorials, reference sheets

• 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
• 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

Websites

• 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.