If you're creating your own logo I'd suggest using some vector based software instead, i.e. Illustrator instead of Photoshop. If you want open source software, try Inkscape. The learning curve isn't too bad and it's worth the time to save yourself potential future headaches in creating promotional materials for your business. Specifically, in vector format your logo will retain its resolution regardless of how large you blow it up. You can take your vector based business card logo and turn it into a nice sharp highway billboard, whereas a rasterized image like what Photoshop creates will pixelate horribly. If you ever need to use the logo in other software, you will generally get better results converting from vector to raster than vice versa.
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