Until recently, there have only been a few thunderbolt external hard drives and they are quite expensive. I have recently purchased the LaCie Little Big Disk 2 Terabyte disk array. These are medium priced spinning drives. The solid State ones are considerably more expensive but offer much higher Reads and Writes. I was look for a drive that was faster than my Firewire 800 solution for Final Cut Pro 7 and X editing. To install the Thunderbolt drive all you do is plug-in the Thunderbolt Cable to the Mac and the drive. Then I plug in my external monitor to the drive. I am getting good Reads and Writes with this drive. Here is the Blackmagic Disk Speed Test of it on my 2010 MacBook Pro.
Compare that to a single 2 terabyte Seagate GoFlex Firewire 800 drive. As you can see the LaCie Thunderbolt is a lot faster. This means your video will play back a lot better and will drop less frames. These drives are small and can be toted around for location work. Do mind that it does have an external power supply. I have found that the drive does not go to sleep when the Mac goes to sleep and that there is some noise from the unit mainly because of the fan. If you are looking for a small moderately fast self-contained drive, the LaCie Little Big Disk Thunderbolt drive is a good solution but not that inexpensive. They have proven to be a work horse and reliable.
I have discovered recently that Seagate offers Thunderbolt adapter docks for it’s GoFlex line of hard drives. Many bare external SATA drives can have success docking directly as well. I have many of the full size GoFlex drives already and use them with the Firewire 800 adapter. These new adapters for thunderbolt are very frugal to use. They don't cost a lot and you can get bare drives very reasonably as well. It will save you some cash in the long run, and you’ll be able to expand by just using several drives. It you choose SSD drives for these adapters you will be able to connect them to the new MacBook Pro with built in Flash Storage. The smaller Seagate GoFlex Thunderbolt Adapter has only one Thunderbolt port so it has to be on the end of a Thunderbolt chain and is designed to be used with laptop drives. It is buss powered so it does need a power brick. This would be great for location work where you want to carry a little as possible and don't need an external display. The full size Seagate GoFlex Desk Thunderbolt Adapter has two Thunderbolt ports for daisy chaining with a monitor and a power brick.
The video below shows a Vertex SSD Drive docked directly to the Seagate and taking full advantage of the amazing Read and Write speed of the Thunderbolt interface. This is a very frugal idea for much greater drive speeds.