Useful resource for typography

Thanks to the Google Personalized Homepage's new "Recommendations" feature, I found the following website:
Identifont
It allows you to either
a) Look up a font face by name
b) Look up a font by distinguishing features

B is time-consuming as it asks you to examine all the details possible on the font - the style of the lowercase 'g' or uppercase 'K', or how many lines are in a $, etc.
I haven't tried it out on any fonts in particular, but it looks extensive and possibly quite powerful, if you're trying to figure out a font someone else has used - or at the very least find something of a similar vein.

In either case, it'll return a graphic of the font (showing alpha characters) as well as information on the font and where you might be able to purchase it.

Nifty!