Google Motors?

Google is testing a new service that will make it easy for people to post and make searchable any content - including used car ads.
The "Google Base" service (check out this post on Download Squad for a deeper explanation) will support all kinds of content, as Google suggests in this Google Base page. Notice that "Listing of your used car for sale" is one of the examples.

Also think about the tie-in to Google's main search index, and its services Froogle and Google Local. This could put the final nail in the coffin for classified ads. Of course, there's a lot to be done before it equals or surpasses Craigslist, but still…