http://www.webdesignerdepot.com/2008/12 ... fy-a-font/
WhatTheFont & WhatFontIs are always great starting points, but when they fail I've started asking on the Typophile forums and so far they've identified almost everything I've thrown at them. The hardest thing to do is wait for an answer though when you are ready to start on your logo.

Now I just move on to the next and come back after I get an answer. If not I buckle down and trace out the text as a path.
Here's a video I made a while back that goes through the process of using WhatTheFont to identify a font, and using it's results for your image if you don't actually own the font.
Make sure to have a look at the tutorial on Identifying fonts as well.