The best thing to do, is as Bman said, delete all the white areas. Then export it as a gif. If you want really good stuff with transparency, Fireworks MX 2004 is an incredible piece of software. It can handle almost anything, and in some cases, does a much better job of resizing than Photoshop. Files can be exported to a custom files size as well. Exporting as a file is no problem either.
You might like to download the trial version and have a look at it. I bought Fireworks MX 2004 the other day a I am throughly pleased with it! On the "small files for the web" front, IMO, it beats Photoshop by many miles.
Cheers

Jonathan
