Doug Neumann [MSFT] has released a great little whitepaper called Guidance for Structuring Team Projects on CodePlex. It's a great read if you're still getting started with Team Foundation Server and can't decide how to structure your team projects and source control.
Back in early February, I wrote a post called Team Foundation Server: Project and Source Control Structure where I explained how our development team had decided to structure one ongoing project. I'm still not sure we're using the best project structure (we create one team project per major "application" we are working on) but so far, it works just fine.
We've also decided to start looking at the TFS Orcas Beta 1 bits now rather than later. It's our hope (after viewing the recent Channel 9 video) that the new features in TFS Orcas will help us manage our corporate development efforts with less time spent on management and administration and more time on development (the fun stuff!).
I'll let you know how it goes!