Two really handy online tools to help you identify a font.

http://www.identifont.com/
This one works by asking you a series of questions about the letters of the font, eventually coming up with one or a handful of suggested fonts. In my experience it is very accurate.

http://www.myfonts.com/WhatTheFont/
Here, you upload an image of part of the font in question and find the closest matches in their database.