Is anyone here on Wheelwell.com?
I learned about it the other day on the SmokingTire Podcast and decided to check it out. It's a car "social network" at its core which is fine. What I really like about it is you can log all your service, modifications, tuning parameters, mileage, etc. and keep track of everything in a central location as opposed to the small notepad I keep, and then lose, in all my cars.
I'm just getting started on it but it seems pretty cool. Its not like Facebook or twitter where you can waste hours or feel like checking it regularly but its a good place for car enthusiasts to at least post mods.