What the Font is a website that lets you take a screen grab of text and identify the font used.
They now have an iPhone app you can use to take a picture of a magazine, book, etc and identify the font used.
If this doesn’t excite you then you are not as big a design geek as I am.
http://www.macrumors.com/iphone/2009/02/11/whatthefont-comes-to-iphone/