I am well in to the process of using Afternic.com escrow on a new purchase and it seems like a real good service thus far. Also used them last year and that one was successful and fast. This is taken from their website:
"This service will present your offer to the owner and help you negotiate the best price, even if the domain name is not listed on Afternic. You remain anonymous until an agreement is reached. After a purchase agreement is reached, you send your payment to Afternic and we do not release the funds to the seller until the domain is safely transferred to you. This DNescrow? process guarantees that you will receive the domain or a complete refund. There is a $1 fee to join the exchange."