LogMeIn Hamachi is a zero-configuration virtual private networking (VPN) application.
In other words Hamachi is a program that allows you to arrange multiple computers into their own secure network just as if they were connected by a physical network cable.
Hamachi is fast, secure and simple. Its core version is also free.
If you don't have your firewall setup or if you don't know your IP address or a bunch of these other barriers Hamachi is here for you. I think this is great for people who don't have Groove to sync their notes and they want to directly access their home computer. Even if you have Groove or FolderShare there are some things that you would like such as: remote desktop without any hassle or sharing your iTunes music library and more. I think they are just lowering all the barriers to doing this which for the übergeek is common practice but still too much work. Anyhow check them out: Hamachi.