Classified Intelligence reports briefly in a press release that Google is looking to include listings from classified advertising web sites in its search results. Via Threadwatch, Paid Content gives a little more detail on the Classified Intelligence news, that Google is looking to take in direct feeds of classified content. For some perspective, many of these listings will already be within Google's regular web search results (and Yahoo's, and MSN's, and Ask's).
However, taking in feeds would allow Google to do make it easier for searchers to sort and filter in various ways, just as feeds have helped with that on Froogle. Even with without direct feeds, you can still do a lot of mining of the web to build classified listings through crawling. Oodle is just one example of that.