You Software has said that they will not be developing You Control: Desktops any further. It does not work with Snow Leopard and there are no plans to do anything about it.

What a shame - the app is indeed what Spaces should have been. I am now forced to use Spaces and I am finding it very clumsy in comparison.

There appear to be no third-party virtual desktop apps - a great pity given the Unix underpinnings of OS X.