Can Spaces be configured by project, rather than by application? Spaces seems to give you a choice of having a given software application open in a single space or in all spaces. Is there a way to configure Spaces to so that each space is devoted to a particular project, regardless of what applications you happen to be using for that project? 

For example, in Space 1 I might have Word files, Excel spreadsheets and a browser window devoted Project A. In Space 2 I might have a separate set of Word files, Excel spreadsheets, and a browser window devoted to Project B, etc. That way I can switch between projects by simply switching spaces, rather than having my screen cluttered with all of my projects at the same time. 

If Spaces can't do this, does anyone know of other ways to create this type of functionality in Snow Leopard (or Lion)?
What I've done to achieve this is to simply not assign any applications to any special space at all. That way, when opening an application, it opens on the space I'm curently on, letting me organize my work into different projects as I want.

On Lion, the organization is kept through reboots, at least for some applications. 

There is also the utility Moom, which lets you save configurations of different application windows to easily recreate spaces you use often.