Hate repeating yourself? Love macros? LaTeX lets you write `beautiful documents' (PDF, DVI, HTML, ...) with macros. It can be a bit tricky to get things just right, but once you figure it out, it's easy to reuse the code.

Take a look at my packages, the Drexel Liki page, the source for most of my papers (if you scroll to the bottom of a paper's HTML, there is a source files link), and my thesis.

If you're interested in LaTeX and graphics, you'll probably be interested in Asymptote and PGF.