Well, I am always finding myself spending a couple hours fiddling with fonts for each new design I come up with. In fact, I spend so much time that I thought I might code something to compare different fonts.

WAIT!

Did you forget to google it first?!
(...oops - I guess I did...)

Ok, so after coming back to my senses (and using google to avoid re-inventing-the-wheel) I found two sites I really like:

http://typetester.maratz.com/ [1] (full-featured AJAX site)
http://xiapdesign.com/testyourfonts/ [2] (Simpler alternative)

Remember, don't make your main content text 10px! 11px is the minimum.
(unless you have some re-size widget.)

More...
http://webdesign.maratz.com/lab/fonts_table/ [3]
http://www.thenoodleincident.com/tutorials/typography/index.html [4]