For those of you who think USB thumb drives are too big to be constantly carried around, the tiny iDisk Diamond is your best alternative. It is a fully functioning portable USB drive, which just happens to be the size of a fingertip, and has 128MB of storage space.
Also, the iDisk has a small hole at the top so it can be easily attached to your key chain.
The iDisk Diamond costs 79USD, and is available at Dynamism.com