Thanks for the thread--I've been lurking for sometime. I will ride in the "Hell of the South" training race this Saturday (http://hellofthesouth.wordpress.com/) which is my first race in a long time and, like Dominae, would appreciate any advice (including "what the hell are you thinking" which is my wife's perceptive advice). Also, since I am far less serious (no coach, modest power numbers, etc) than the regular posters on this thread, I thought my experience might be useful for others, like myself, who are considering dipping their toes in the pool before jumping in. I will post race reports as long as they are not too embarrassing.
I did race one season 10 years ago and by the end of the season I was midpack Cat 5 with one top ten finish. However, back then it seemed much more casual, at least in the middle Tennessee area near Nashville and the races accounted for the most of my training. Since then, I've commuted semi-regularly and done occasional group rides (I got used to being dropped when I tried to do A rides with the local racers).
Last year I started doing some longer rides with the FOGBEES (`fat old guys on bikes'-see http://fogbees.blogspot.com/), a recreational group north of Nashville, which encouraged me to see if I could get in shape to again try some races. I've managed to develop enough fitness to do the Saturday training rides with a local team (Bikers Choice in Hendersonville, TN).
The cat 5 HOS race is about 28 miles and, from the race profile, is pretty flat. I'm 6' and have managed to drop about 15 lbs to 177-180 lb range without much difficulty. I would like to get closer to 170 but right now I seem to have stabilized around 178. Fortunately, my understanding is that the race this weekend is relatively flat, but later races (particularly, the Highland Rim RR in May near McMinnville) do have substantial climbs and hopefully I will have a little more power and little less weight by then.