You leave a lot of leeway between price and quality.
One of the better macro options, IMHO, is the Sigma 70mm f/2.8 EX DG lens. Incredibly sharp and flat focus. Price about $400 US.
If you just want to get some experience at photographing small things close up I recommend the Raynox Super Macro Conversion Lens Set. You can get it on Amazon. It is a set of three diopters with a holder that attach to the front of your lens with a spring clip rather like a lens cover. The set includes 6x, 12x and 24x lenses. These will fit on lens diameters 52-67mm. These are kind of like getting a loupe for your camera.
The price is a little over $100 US. These are nice as you can attach them to a variety of lenses you have. The only downside I've seen is that they magnify a bit too much. The 6x would probably be good on something like a 50mm lens for larger objects.
You can also find other single piece macro lenses that will fit specific size lenses. I have one for another lens that is a 2x magnifier. Works really well. It means you have to be two times closer to the subject but for still life that is not a problem. As in most things, quality and price go hand in hand but these are relatively inexpensive compared to buying a whole lens.
I just did a very quick search and found this page which talks about close up attachment lenses.
http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/A95/Close-Up/Close-Up-Lenses.html