Thanks a lot for all the nice comments guys!
Exactly, its an attachment that just clips to the front of most macro and telephoto lenses via an adapter. Raynox makes even more powerful super-macro lenses but beyond this level of magnification, you usually need to use focus rails and whatnot- I like this one because I can still hand-hold the camera.
The plane of focus is so narrow with this setup that I had to shoot at f/22 and up to get usable pictures.
These were taken using a Canon Rebel T1i with a Canon EF 100mm f/2.8 + Raynox DCR-250. The flash is a Canon 580exII shot through a LumiQuest Big Bounce Diffuser.
Thanks again everyone!
Aaron