I just stumbled across these Macro pictures I took a while ago, and thought I'd share them.
I used 2 lenses for the pics: my 18-55 EF-S (the kit lens I got with the 350D), and the 75-300 lens. The 75-300 was attached to the camera (fully extended mostly), focusing set to manual.
I used a double threaded ring (both sides 58mm), so I could screw the 18-55 in reverse on.
The 18-55 was set at 55, and focused on infinity.
It's not that hard to take pictures, but you really need to use a tripod, at those magnification rates you need
lots of speed to take the picture.
Using 2 lenses (which aren't really great either.. both around f4-5 at maximum extension) means I really needed lots of light.
The best thing to use is a f1.4 50mm lens for the one that gets screwed on, and some way to hook a ringlight to it.