I'm running a dual-monitor setup at the moment. By judicious use of Cygwin/X I've arranged it so that the right monitor is mainly occupied by a full screen Gnome Session over SSH from my Fedora box. It's possible to get the session full screen, but since it involves fiddling with the main taskbar (the session always pops on the main screen, so is initially constrained by the taskbar and doesn't resize when forced onto the second monitor - but you can shrink the taskbar then start Cygwin/X) I'm filling the gap with the trial version of UltaMon - though there's a displeasing gap between the fake taskbar and the bottom of the X-session. Best thing about this setup is the ease of passing clipboard data between the two systems.