Do you enjoy road racing? Good, I do too. What do I do to improve my skills in the cheapest and safest way possible? Go karting. It might seem silly but Kart 2 Kart in Sterling Heights Michigan is one of the best places (In SE MI) to go to fine tune your skills.
I attended an endurance race there last night, 2.4 hours of pure racing. Pulling 1.5+ G's going around corners for 2.4 hours between yourself and a team mate is a terrific experience for anyone who loves road racing. It deserves respect; it challenges your body and mind. The difficulty comes in when you're trying to stay consistent. Our team put 270 laps in, with an average of 26.4 including the three pit stops we made to change drivers. Having a Lemons car and participating in Lemons, this enduro is the next best thing.
Three things that are challenging in road racing exist in karting. The difficulty to pass correctly without contact, the struggle of staying consistent lap after lap, and the smooth factor. Seat time is great, more seat time you get no matter if it's in a race car or a kart; it's seat time that improves your driving ability. So get behind the seat of a kart and have a crack at it. You'd be amazed at how difficult it is to cut 2/10ths of a second off your lap time.