TeX

Making TeX Work: Did you know that Norm wrote a book? Alas, it's now out of print.^[1] Luckily, he's written another!
WWW interface to the Comprehensive TeX Archive Network (CTAN-Web)
Online Help: Online help for Plain TeX, LaTeX, BibTeX, MakeIndex, and SliTeX.

^[1]Yes, I'm planning to put the book online, but it may take me a while to get around to converting it.

nwalsh.com