Yesterday, Rui pointed me to two applications/services that immediately found a place in my Applications folder.
The first is Yuuguu. Its a screen sharing application that just works. You install the client (Windows, Mac. You can also use the web server), create a free account and add your friends (by email address). That's it. You can now share you entire desktop with any of your friends. Essential for those support calls you get from your family members.
The second one is PortMap, a free application from the CodingMonkeys (of SubEthaEdit fame). It allows you to open services running on your desktop when you are sitting behind a NAT gateway. It will use NAT-PMP or UPNP to map a public port to your private address.
PortMap is the end user application. They also made available the Framework they created around the code that does this magic. I should point out that Leopard has this functionality built-in (point from JoÃ£o PavÃ£o, the Cocoa guru at hand).