Well, you don't say what OSs are involved, so.....
For windows, I find that Remote Desktop works as well or better than anything else, although if you pay for the RealVNC version with the mirror driver, that's supposed to be as good.
For off site access for windows, www.logmein.com (the free version) works very well.
If Unixes are involved, then VNC is definitely the way to go, there are various solutions for doing this remotely. Everything from redirection servers, to just forwarding a port in your firewall to an ssh server and setting up the various tunnels.
