There is a great series of races in and around Grand Rapids run by kisscross.com. I managed to get out to a few events and so far have had a pretty good time. Today sucked a little due to some pre-winter flu crap I have but it was still a good course. The courses are between 1-2 miles long usually so these are sprint type events where lap counts can be anywhere from 3-8. The general idea is to go hard and try not to throw up.
If you can ride a bike, it's worth coming out on a Sunday and giving it a go. The last event of this season is on November 27th.