You can try reversing the lens for free before you buy anything.
Pringles Macro
But I'm not sure I would want to try it on one of my lens's. But you can buy a really cheap second hand lens to try it on.
I bought a Sigma Telephoto lens 70-300 for my D50 that can also do some macro. While it can't do 1:1 macro, 1:2 is better than nothing.
Macro Water Splash Set
Andrew