A while back I whipped up a custom folder icon for Dropbox on Windows Vista because I wanted something that stood out a bit more and made it easier for me to find the directory.  I'm not sure what the best software for icon editing is, but I used the only one I could find that supported layers, Pixelformer.  Aside from supporting layers, Pixelform has the additional benefit of being free.

Download it from the Dropbox Icon Project page.

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