If your willing to sacrifice your body cap and your lens cap. You can build a nice macro lens with a pringles tube. You get a snack and a macro lens at the same time!!!!
http://www.photocritic.org/2005/macr...y-on-a-budget/
This guy explains what I mean. I've done this for film photography as I have TONS of caps.
The only thing he forgot to do is spray paint the inside/outside of the can Flat black! He is having a blur problem because of the light bouncing around the inside of the can. It could be reduced by using a a Flat black spray paint with very, very light coats. and make sure it's completely dry! I would also do that before you glue the body cap on!