Identifont identifies fonts by description, partial name or sample
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If you work with the web, you work with fonts, it's that simple. Along with graphics, fonts carry a tremendous amount of emotiveness. Choosing the right font can make or break that feel you want for your site.
Unfortunately, fonts aren't easy to deal with. First of all, there's a zillion of them. Additionally, once you find one you want, it's usually one you have to buy! All those fonts don't come cheap.
So, what's there to do? Unfortunately, I haven't found a way to get the web to tell me "what's a free font that looks like this commercial one?". However, you can describe the characteristics of the font you want to the Identifont service, and it will give you a list of similar fonts, some of which *may* be free. It requires a bit of elbow grease and it's not 100% successful, but I *have* been able to find free font substitutes for the ones I've wanted by using it.
If you're just looking for the name of a font that you have in a graphic, you can use Identifont or the also excellent WhatTheFont! service at http://new.myfonts.com/WhatTheFont/, part of MyFonts.