There is a very cool service called WhatTheFont which lets you detect the font used in a logo or image by just uploading it. All you have to do is either save that image in your harddisk and upload it or just give the image url location and upload it.. it will search the words and give you the possible Font that would’ve been used.
Here’s a facebook test!
Gave the url location for facebook in WhatTheFont
And it showed me the possible fonts that would’ve been used in that logo
It supports GIF, JPEG, TIFF, BMP extensions and for any designer or someone whose uses photoshop extensively.. it’s a “Life Safed” utility =)
WhatTheFont | Official Website