How about turning that classified ad into an article of sorts and put it on squidoo, then submit the rss feed to feedage or another rss aggregator, get it indexed then write another related article, spin it several times and put it on some other high pr sites like hubpages, wordpress, wetpaint etc. linking back to your squidoo for your keywords. Then backlink all your new sites with some good bookmarking, not your squidoo, to raise your main site (squidoo) to the top, and at the same time having numerous other listings at the same time. You can dominate your search term with some of the better classifieds, but it only lasts so long, especially with F'n flaggers, unless you continuely monitor them or mass submit. Squids are easy to update and keep fresh, not like writing a hundred "diff" ads to not leave a footprint or dealing with related ad roadblock. Not knocking classifieds in anyway, just seems like a young mans race anymore.
Just little bit of my 2, but you can find some good autoposters for classifieds, not sure how long they last with the constant changing of some high pr classifieds like CL.