Other than the Ravage USB drive, here are the Trypticon and Grimlock transforming laser mice, which are now available for pre-order. These mice have 800dpi resolution and three buttons. They use USB interface.
Trypticon and Grimlock are both priced at $59.99. Like the Ravage drive, you can get Collector Grade packaging with extra $2.
Along with the mice, there are also Tigatron Transforming 2GB USB drive ($42.99) and Blaster Transforming USB hub ($59.99).