I've been playing for over a year now and it's been the best free web based game I've ever played and I have plenty of experience in that area
Initially you choose your driver, setup a team (coach, mechanics, race engineers, etc) and start from the bottom, usually Fórmula 3. Then you move up the ladder to F2, Indy, Nascar or even F1! It's quite literally a motorsport career management simulator.
It's easy to setup races, pretty intuitive and has a great community. Give it a shot:
http://www.myracingcareer.com/r13358/