Hey robo mantis
Cameras are something I can talk about! lol
As the market stands you probably want to go with Canon because their bodies give a lot better performance than Nikon bodies. Nikon picture tend to look more "flat" compared to the Canon equivalents. They also have a wider current lens selection which is more important.
Canon has a great variety of macro lenses. You actually should plan to spend more money on your lenses than the body that you buy because the lenses really make the picture.
Also, if you have the money, you may want to invest in one of the professional instead of prosumer bodies (the Rebel line). Especially in the Canon line this adds a lot of extra functions. The most important of these added functions for macro photography is "mirror lockup." It is where the mirror that usually flips up on the SLR while taking the photo, flips up beforehand to minimize vibrations conducted to the sensor.
Also, you need a tripod and flash(es).
If I may reccomend a body: go with the Canon 20D (~800), which is a great camera. Or the 10D that you can pick up used for $500-ish. Don't spring for the 30D because there is no technical advance since the 20D (just a bigger screen and price).
Then go for the 100mm macro lens Canon offers (~$500). Or, to spend less and get used to taking photos get the "50mm compact macro" (~$250). It has half the magnification of the 100mm but can be upgraded later with the "lifesize converter" to get full macro.
If you get really adventurous later on you can get the MP-E 65mm 1-5x which is a specialized macro lens that can fill the photo with a grain of rice on it's 5x magnification!