Are you tired of overly-smart word processors, too? In september 2001 I was introduced to LaTeX by a well-meaning friend and I personally can never go back to MS Word or Star Office again. It's just so practical, stable, controllable, configurable, neat, sexy nerdy - yes, anytning you would want! (Do I sound enthusiastic?)
First, you need the tools. MiKTeX provides an implementation of TeX that is ready for download for just about any operating system. Get it now!
A good place to get started is David Wilkins "Getting Started with LaTeX" website. Wilkins is a lecturer from Dublin University who has spent quite some time making this beginner's guide for LaTeX that will get you started right away.
When you are done with the first introduction, you should read the "Not So Short Introduction To LaTeX2e" by Tomas Oetiker et.al. It can be downloaded in various formats from:
The research project LaTeX3 Project provides many articles, documentation, bug reports and a most useful FAQ (Frequently Asked Questions). I particularly used the FAQ in the beginning.
Naturally, the complete LaTeX2e reference is nice to have handy. It can be found at multiple sites, one on which is listed below:
For typesetting graphs and diagrams directly in LaTeX I can really recommend XY-pic. Great for state machines and much more.
Although there is much material available on the web (use Google to find more) there are also some very useful books around. I have Lamport's "LaTeX - A Document Preparation System" but really also ought to buy "The LaTeX Companion" by Michael Goossens et al.