Well, since you are not really in the market for one, you might as well grab an el-cheapo fisheye off of eBay to whet your appetite. If you like what it does, then you can think about a higher quality image from a more expensive version.

Eg. there's this $30 "fisheye converter lens" that screws onto a Canon zoom lens (58mm front threads required):

http://www.ebay.ca/itm/New-Super-Wide-HD...=item19c3e5066d

And there are other, similar converter lenses that fit other front thread sizes.

Cheers