We were thinking about organizing our BIG project this way:
\\trunk
[CompanyName]
[Product1]
[Project1]
CompanyName.Product1.Project1.csproj
An alternative that I've used is to have all my solution files in the same directory.
\trunk
[CompanyName]
CompanyName.Product1.sln
CompanyName.Product2.sln
[Product1]
[Project1]
CompanyName.Product1.Project1.csproj
[Project2]
CompanyName.Product1.Project2.csproj
[Product2]
[Project3]
CompanyName.Product2.Project3.csproj