Please see my blog for a full list of tips and advice on how to rent to own a house
I'm not aware of any site for rent to own homes. These situations are fairly rare and not always a great deal for the buyer. Most buyers seeking rent to own have credit issues. For a seller to be willing to accept the credit risk they must be receiving a benefit which balances out the risk. This is commonly over market rent, large upfront fee/deposit and a price which favors the seller.
If you decide to pursue this, find a local agent with experience doing these. This is a specialty and you don't want to be someone's guinea pig.