gDisk:

gDisk is a little tool that lets you use your free space on your GMail account, as an extra hard drive. This is the first release (0.1) so still it’s lacking hard of features like drag n’ drop, progress bar when uploading, and a Delete and Pause button for your uploads to name a few. GMail also have a 10Mb file size limit, so your not looking at a replacement for your .Mac account either.

(Via Cool OSX Apps.)