Knuckler, if you have access to Adobe Illustrator, it's very easy to add text along a path (such as a circle) and export that to Photoshop.
If Illustrator is out of your price range, you can always use
Inkscape, which is open-source freeware. The current release (0.40-1) has a feature that allows you to place text on a path...you can then export the file as a (transparent) PNG file, which you can open up with Photoshop and add to your logo.