Here's something logical, Leasetrader.com is a site where credit-approved folks looking for short term leases on cars can take over for people wanting to get out of their leases.  Sign me up for something like that for houses (I guess that's called Craigslist). 

People always make fun of some social activities that Bubble 1.0 companies tried to turn into web services (grocery shopping, buying rubber balls, etc.) but there are some transactions that clearly make sense.  I found Leasetrader over at Lifehacker, but it's been around for years (see it in the Wayback Machine).  Chalk this one up as a point for the Old School.  (left: Leasetrader.com branding circa 2001)

It's also an example of a niche that a general purpose listing site can't fill.  It needs lots of info on leases, getting out of them and credit.  Plus there's probably a large group of people looking to lease a Mercedes who don't want to smell the patchouli  over at Craigslist. (right: Leasetrader.com branding circa 2006, check the rounded corners.)