I juts got a macro tube in the mail. It’s basically a dumb (ie you need to be on full manual mode-no metering or AF) piece of aluminum that moves the lens further away from the camera body. Doing so it decreases the minimum focal point.
Basically it means you can get really tight up on stuff and shoot close ups. Here are a few test shots
The macro tube has 3 different sized rings that thread into one another. That way you can roughly control the distance between the lens and the camera. The three shots are taken with the three rings on. Here’s a photo (ripped from deal extreme)