We were thinking about organizing our BIG project this way:
\\trunk [CompanyName] [Product1] [Project1] CompanyName.Product1.Project1.csproj
That looks pretty good if you ask me. Especially naming your projects by their full name including full name space part. I've found this helpful when there are numerous projects, especially if there happens to be similar projects across different products.
How and whether you split on product and project (where I assume project is more like an application than a solution project) is very much down to the size of your organisation, it's make-up and your preferences.