TODO - check out http://scruss.com/
See also Remote desktop with the Raspberry Pi
possibly coming later
xpra is similar to rdesktop, except it lets you run single application windows instead of a whole desktop environment. It also lets you "detach" from the session, so the applications you run will stay running on the Raspberry Pi when you turn off your other computer.
This would be idea, but I cannot get this working properly. At some point I had the Raspbian repository xpra working, but now I can't even get that version to exist. It says it installs, but it doesn't exist on the Raspberry Pi or my desktop.