This is the thread where new versions of racer are announced.
Most recent stuff related to racer goes on on forums. People share cars and tracks there, show off their wip's (work in progress) and seek advice/help/comments.
The racer section on rscnet can be found here.
A good source for cars and tracks can be found here on racer-xtreme. It is a database of cars/tracks where users can give feedback and can rate the work. Unfortunately not all people making cars/tracks use this site.