What about cash by certified mail using a 2 of 3 multisig transaction with an arbitrator. Certified mail is fairly inexpensive and if you are doing larger amounts you can do registered mail with insurance.

I sold some btc and received cash via certified mail and it worked out perfectly.
If there was a problem, like the guy never sent the cash...I could just refuse to sign the multisig and the btc would not go the the buyer.
The arbitrator would be called in and then he makes a decision where the btc being held in the multisig address will go based on evidence provided by both parties.

It takes a lot of the risk out these types of transactions.