You can see the fonts that the pages call out for in the Common Theme CSS and the user CSS (I use the Green web-safe theme: Green Web-Safe CSS).

I believe Petruchio came up with this list of fonts a few years ago. You should be able to find most of them freely, such as http://www.abstractfonts.com or http://www.goodfonts.org. (Disclaimer: I have no relation to either of these sites.) Or substitute whatever you like in your user CSS.