I published a new Android application to the market today: CraigsHome. CraigsHome plots CraigsList rental listings on your Google map. You can get more information about the listing including photos, and even email the author right from your device with one click.
Right now, it only covers rentals (apartment, room, house). It could easily also cover for sale listings. Without going into too many details, it would require some extra processing on the back side. With for sale listings, this could be the Zillow-killer app. Re-presenting data from CL is never going to be as clean as Zillow listings, but with the popularity (and free-ness) of CL, it could really put a dent in things for them.