One of the main things to keep in mind when riding in the rain is the center of the lane, especially at intersections will be really slick. The traction is in the wheel tracks of the cars.
Also watch for places where they smeared tar all over the road, there is zero traction there. On a certain downhill offramp with a stop at the bottom here in akron, the entire road is just one big sheet of tar. The first time I came down that off ramp in the rain i was in for a real shock. It would have been nice to have ABS at that moment, I was intermittently locking the front and rear. No traffic so i rolled through the stop sign due to the truck barreling down from behind, I sure wasn't trusting his ability to stop.
I actually enjoy riding in the rain quite a bit, especially when i have the road to myself. Powerslides, rolling burnouts, etc... It brings out the hooligan in me.
Probably the biggest danger of rain riding is the other cars, they can't see shit when its sunny and clear, its even worse when visibility is limited.