Bryan,
I have the Raynox DCR-150. It's very good.
Allows you to do macro with just about any lens that it fits. Been using it with my superzoom (FZ-50) and a 70-300 zoom on my Canon 20D. I think the 250 is equivalent to an +8 diopter and the 150 about half that. For a superzoom its great, much better than the diopter rings and just snaps on the front. Probably not as good as a dedicated macro lens on a DSLR (I don't have one) but it doesn't cost as much either.
Here are some examples with the superzoom.