Often multiple applications share a large codebase of libraries that change often in development. In these cases, I prefer to create a solution named after the suite, and i
It really depends on your organization's particular needs. MSDN has a good page that goes through the various recommended solution layouts, including:
The MSDN page also discusses the pros and cons of each model in more detail so you can decide which one makes sense for you. :)
In general, for an application suite such as you describe, I would consider the partitioned, single solution model. There's a single master solution that builds everything, and a number of separate solutions for each individual application within the suite (assuming the applications are of appreciable size).
If the applications in the suite are small and build quickly (e.g., a suite of command line tools), I might not even generate the separate solution files. That's really a judgement call we can't make for you. :)