I've got a few machines at home and I want to use Remote Desktop to connect to them when I'm out and about.  Well one is easy enough to set up if it is either directly connected to the internet (possibly a bad idea) or if you have a wireless router with a firewall and other management features (much more secure).  I have the latter and I set up a rule to forward remote desktop traffic on TCP port 3389 to my main desktop.  But I also have a server I would like to get to.  No problem you just need to change the port that Remote Desktop uses in the registry.  Just go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp and find the PortNumber entry and change it to the port you want.  Make sure you edit it as a decimal by choosing the decimal base.

Here is an easy article on setting up multiple machines for Remote Desktop access.

Check out the article for a lot more info.