I have setup CruiseControl.net for a bunch of my projects which are related. As a result a single project tag in CruiseControl has multiple SVN checkouts and then a bunch o
There's a task to do just what you're asking about.
You'll need to install the MSBuildCommunity tasks, found here.
Then, you can create something like this:
$(CCNetLabel)
Note that you can set a build number prefix in your ccnet.config file so that your assemblies will be numbered 2.1.0.x where x is the build number. That's how we do our version numbering where I work.
You'll still need to keep a default AssemblyInfo.cs file as part of each of the projects that make up your solution.