If you're running a computer that has ssh capabilities away from home, this is easy:
1. ssh -l <yourusername> -L 5801:127.0.0.1:5801 -L 5901:127.0.0.1:5901 <yourserveraddress>
2. Make sure the home machine is running a vncserver
3. Start a vnc server locally.
4. Run a vnc viewer program that connects to your LOCAL machine (127.0.0.1) and use the password specified on the server at your home.
You can find all the programs you'd need in various OSes at http://www.realvnc.com
This works for me from work in Mac OS X 10.3. Not sure about using Windows, but I'd bet you could do it with puTTY too. Anyone?
Edit: The reason I use ssh here is that it tunnels your connection through ssh, making it a secure connection. No eavesdropping. If you didn't want to do it this way, you could probably just get a viewer for the away-from-home computer and connect directly to home. This isn't secure, and passwords etc. will be sent in the open if I'm not mistaken.