I recently bought a Cisco 7941 phone to run SIP with and ended up on this site looking for help as the phone had no documentation. It wasn't as easy to configure as I had anticipated as the new series phones are not configurable in the same way the old ones are.
I spent over 60 hours googling, packet sniffing and analysing how the phone works, and wrote as much as I can remember up for others to be able to get their new phones working without having to go through the hassles that I did.