I used Shipbikes.com when I sold my Venge. GREAT service! Just as advertised. I used the UPS option. The box I bought from Shipbikes was excellent! The bike arrived at the buyer's without any damage.
The Shipbikes service is basically the same as using UPS or FedEx, except you get a nice discount through the Shipbikes account with the carrier.
It's a great concept, and works flawlessly. The boxes they sell come with extras that ensure that you can pack your bike really professionally. I took it one step further and wrapped cardboard around all the tubes of the frame.
If I should have the need again, I will definitely be using them again.