One of the challenges of macro work, especially as it pertains to insect photography, is getting sufficient and well-distributed light into the tight area where your subject is. This is my 2005 rig. Lens is the Sigma 105 DG

I usually mate it to the Tamron 1.4 converter, as I've done here, although I sometimes use Kenko tubes.
Light is provided by two non-dedicated units:
Nikon SB-24 is the key light
Sunpak DX-8R is the fill

I'm non-dedicated mostly because I don't have the resources for dropping about 700 bucks for the current dedicated equivalents. However, for those of you who think that dedicated is the only way to go, remember that manual (variable fraction) output provides absolute control over lighting ratios, and the exposure is never fooled by white flowers or other hightly reflective subjects. Also, when shooting macro, you tend to work at fixed distances; you know what kind of reproduction size you want, and move your camera to focus. Forget AF for macro. It's just not practical.

The bracket, which is an old Sunpak as well, lets me position the key light right where it's needed. The key light's zoom head is zoomed to its widest angle to spread the light about.
My ratios are:
Key light (SB-24) fires at 1/8th power
Ringlight fires at half power

Using these ratios I find that shadows are still visible, giving nice modeling and natural rendering.

The ringlight, which is mounted to the D70's hotshoe, is triggered by the camera. I have a slave mounted to the end of the ringlight, which triggers the key light.

My daughter says the rig looks like ghostbusters. My wife keeps encouraging me to shoot in the backyard, not the front yard.