I use both a Wolverine 80GB FlashPro and a 40GB Smartrax FlashTrax.
The only difference besides drive size is I can see the images and watch movies on the FlashTrax. Also the Wolverine is slightly faster on the card to device transfer speed.
There are many of these devices including Epson, Vosonic, Wolverine, Jobu, Hyperdrive, NexTo, and Delkin just off the top of my head each with several variations. Oh and even a Canon one supposedly.
You want to look for cost, reliability, capacity and transfer speed (card to device is most important) and then look at other features such as seeing the images, file transfers, music, videos etc..
And Suzie you should see how fast a 2GB card gets eaten up on my 1DsMkII