I'm not entirely sure what you mean by social/map site to be honest. If you want to record your rides and follow friends/pro's to see their stats etc then http://www.strava.com/.
If you are looking for a site to find new routes that other people in your area cycle then I'd recommend http://ridewithgps.com/.
Posts
If you are looking for a site to find new routes that other people in your area cycle then I'd recommend http://ridewithgps.com/.
I use the two the other replyer stated. I'm also prefer to use Garmin Connect over them as you get Segments to work within your course.
Bike route toaster is also another popular site. I used to like this one but stopped using it in favour of ridewithgps.