Installing linux to an external hard drive.
 

I am looking for a distribution that I can install on an external USB 2.0 hard drive. Is that possible (I'm pretty sure it is, given all the devices linux can be installed on), would it be easier to run a live linux distribution? Any helo would be appreciated, I would like to have the external hard drive bootable as well.

Any how to instructions posted anywhere would be awesome. Thanks!