Chapter 8 of White Space is Not Your Enemy deals with type. We've talked about different fonts quite a bit, but this chapter goes more in depth. It explains glyphs, the parts of a font, types and characteristics, and when to use which type of font. To go deeper, it even gets into kerning, leading, tracking, swash alternatives, ligatures, and typesetting. If you've ever been formatting some text for a project and realized it was almost but not quite right, those are things you need to learn to make the tweaks to your copy that will perfect it. You'd be surprised how much additional spacing between letters, a few alternates, and better leading can improve readability in layouts and papers.
Another good bit of advice is to avoid overly used fonts. Just as you don't want the same design or content as everyone else, you don't want the same font for your headers or logos that everyone else is using. (This doesn't imply to invisible fonts for copy, such as Arial.) For example, this font is everywhere. (No, really.)
If you're in need of some more good fonts, I suggest DaFont.com. It has tons of fonts that can easily be sorted, searched and downloaded, and includes the licensing information. If you want to sell your work some day, pay attention to those licenses. Some font makers license their work only for private/personal use, some don't care what you use it for, some only want credit, and some want a payment if you use the font for a commercial purpose. It's usually pretty cheap... and if you're going to make your buck using their work, they deserve the $10 for the work they put in the obviously good font.