Here's the Ars Technica article talking about the project; Google's Getting Started page, which describes how to use the fonts on your page (which turns out to be really easy); and the Font Directory itself. Personally, I'm especially enamored of the IM Fell font, which is just the sort of rough-typography font that I'm always fond of for SCA use -- readable, but with a sort of hand-printed feel.
Important caveat: I think this is all using the emerging standard for web fonts, which means that it requires a modern browser -- and I believe that specifically excludes all versions of IE to date. My impression is that this stuff will work in IE 9, but that's not going to be released for a while yet. So it's questionable whether you can use it for commercial stuff yet, but it sounds entirely plausible for personal pages...
