In September 2009 I conducted a three-hour workshop on LaTeX on Morgan State University in Baltimore, MD. Here you can find some supplementary material I prepared for that course. You can think of it as a collection of most basic things a beginning user of LaTeX (and a mathematician) might need. Probably the most important part is called Further reading—a small set of documents that might be especially useful for a beginner.
Of course, if you want to use it, feel free to do so; also, if you have any suggestions on how to improve it, I would be glad to hear from you. Notice, however, that I want to keep it really minimal, so I won’t include too much.