In Windows Seven, I've been using Dexpot, and it does almost everything I want.

However, It's unfortunate that Jan Tomasek's "sdesk" application no longer works. He stopped working on it a little more than a decade ago, and it continued to work all the way through WinXP, but now it just fails to work in Win7. For desktop managers on Windows, that was my favorite. Dexpot works pretty well, but it still is missing a couple of features that worked well in sdesk.

The current beta version of Dexpot has some support for multiple monitors, but I haven't tried it.