http://www.myfonts.com/WhatTheFont/

Tip: WhatTheFont supports most common image formats, for example GIF, JPEG, 
TIFF, BMP. The maximum image size is around 360 x 275 pixels. The ideal letter
 height for the best search result is about 100 pixels. Try to get the text 
horizontal and make sure letters are not touching. WhatTheFont will only recognize uppercase and lowercase letters.