Denis Bauer blogged a way of adding
custom summary information about your objects into the watch window.
You'll notice that when you look at a collection, instead of seeing System the name
in curly braces you see {Count=X}. It turns out that if you edit the C:\Program
Files\Microsoft Visual Studio .NET 2003\Common7\Packages\Debugger\mcee_cs.dat file
you can display the properties of your custom objects too.
Here is an example of an entry in the file:
<System.Collections.Hashtable.bucket>=key=<key> val=<val>
From that it's pretty obvious that the format of the entry is
<Fully Qualified Type Name>=description=<Property to Display>