I've been using an ancient virtual desktop manager called Yodem3D. It works OK, but it is beginning to show its age lately.
So the 4SysOps blog had an article on a few to try (see comments too)-
I tried Windows Pager http://sourceforge.net/projects/windowspager/ and it works OK. Another mentioned is http://virtuawin.sourceforge.net/ that looks like it might be better. I'll give that one a shot later. If you know of any better ones please let me know in the comments! Thanks.