Here's my blog posting on how to find rent-to-own homes: http://www.trulia.com/blog/don_tepper/2010/03/how_you_can_fi
The main point is that while you might find a few listed on the MLS that way, most won't be. So you have to figure out from other listings which ones are good candidates. There are also a lot of ways to find them away from the MLS.
One of the ways is by searching on Craigslist. My blog tells you how, and it's not just by searching for "rent to own." Here's a link to at least 5 of them: http://duluth.craigslist.org/search/rea?query=lease&catA
And here are another half dozen:
And a couple more:
And those are just from using one of the 11 techniques in my blog.
Hope that helps.