This piece from PhotoGeek on the new Drobo USB four drive storage unit.
This could be a very handy bit of gear and we have contacted Drobo to see if we can get hold of a few of these for re-sale.

The Drobo is unique in that it can have drives of unequal size inserted and removed as your requirements change. Have two 500 GB drives and a few old 100 GB drives when you start then just replace a 100 GB for another 500 GB. Drobo will release the extra drive space as storage on the fly, even while the drive is being accessed by a computer.
I am thinking this will be a useful device for photographers with ever increasing storage requirements. It also acts as a hard drive redundancy system so that in the event of a drive failure no data is lost. All you need to do is take out the dead drive and replace it.