RemoteX is a free Skype plugin that gives you full two way desktop connectivity between remote computers. Works with both Mac and PC, and you can also share photos, web surfing sessions and generally hang out together. You even get a built in laser pointer.
RemoteX is a powerful new application that allows you to share your desktop with another user while on a Skype call. A lighter version of our standard-setting RemoteCall 4.0 remote support software, RemoteX downloads and installs in minutes on any Windows PC running Skype (or Intel Macs with virtual Windows machines) and provides instant access to desktop sharing.
I like how running it in parallels or vmware makes it mac compatble :) nevertheless sounds pretty useful will have to give it a whirl
eeevpn over skype tunnel also supports remote desktop
But eeevpn is not free.