Image by Stewf via Flickr
Font Squirrel also provided a link to this cool What the Font tool. If you've seen a font somewhere but you don't know what it is, you can upload an image and they'll find the closest matches in their database. If that doesn't work, you can submit your image to the forum and have font geeks all over the world help you identify your font. This ought to come in very handy, because I'm really bad at recognizing fonts. They'll never confuse me with a font geek!