Quoted from PNorth:
1. Create a new bank account.
2. Have the buyer go to a branch of your bank and deposit CASH into your new account.
3. Transfer the funds into your regular account.
4 Close out the new account.
If the buyer deposits cash into your account, they can't withdraw it back, and the bank can't hold it. Safest, least expensive way of doing it from my experience.
note that with new FDIC regulations, people other than the owner of the account cannot deposit more than $500
I believe that transfers between banks can still occur, but you just can't have the person deposit directly into your account (the full amount) any more