A few weeks ago I wrote an article about Seagate's thunderbolt drive adapters working with regular SATA drives of SSD drives. These Thunderbolt adapters are listed to work with their GoFlex line of portable hard drives, but here Carl Pendle from www.carlpendle.com shares a video showing that it does indeed work directly with a few other bare drives [Thanks Carl]. For more information, you can find that original article about these Seagate Thunderbolt adapters (here).
If you have to share files, or even edit from an external drive, you can't beat the speeds of Thunderbolt, but options have been very expensive. The SeaGate adapters seem to be the best bet right now allowing you to expand by just purchasing more off the shelf drives.