Escrow.com is the most popular escrow service for sure but they don't take possession of the domain and some people consider this a deal breaker.
The process is pretty straightforward.
1) You and the buyer both need to have an account at Escrow.com. Ask the buyer to give you his Escrow.com email address, log in and initiate the transaction.
2) The buyer will have to make the payment after confirming the transaction.
3) After Escrow.com confirms that the payment has been received, you'll be instructed to send the domain to the buyer. Again, Escrow.com doesn't take possession of the domain, so you will have to send it directly to the buyer.
4) After the buyer receives the domain, he has to log in and confirm so that Escrow.com can pay you.
That's pretty much it.
Some companies like Sedo.com take possession of the domain and that adds an extra layer of security to the transaction. So instead of sending the domain directly to the buyer, you send it to the escrow company and they ultimately send it to the buyer.
Aside from Sedo.com, I used Moniker's escrow service in the past and I used EscrowDNS.com as well. Not sure what to say about EscrowDNS.com, I had no issues with them whatsoever but the previous owner sold the site and I don't have any recent experience with 'em.
eCop.com is a newer escrow company, it's owned by the person who runs Domaining.com and he has a great reputation.
All in all, I'm pretty sure Escrow.com is the best solution for you.
If you don't like the fact that they don't take possession of the domain, try Sedo.com, eCop.com or Moniker's escrow service (it's been quite a while since I used Moniker's escrow service but they're obviously a legit company, the initial owner sold Moniker to Oversee and they ended up selling it to Keydrive recently).