Not sure how many people remember the old Terrarium application, but it is making a comeback. This time, as a project for and by the community.
You can get more information on the background and what this application is by reading Reintroducing Terrarium, now with 2.0 goodness! This is also mentioned by the Windows SDK folks on their blog, .NET Terrarium 2.0 source code now available! and Scott has posted Learning Opportunity - .NET Terrarium is back!
As you may have guessed from the title of that last post, this is now a codeplex project meaning you will have access to all the source of the project and be able to help shape the future of it. The first link above has a list of initial updates that they are considering but since it is up there now, who knows where this project will go.
This is a great opportunity to get to look at some very useful .NET code and see how these concepts can be put to use. I invite everyone to take a look and hopefully learn something from it.
If you want to see a sample of how to write a creature and debug in VS, check out Terrarium .NET: Introduction to Creature Development and Debugging Terrarium with the VS IDE but keep in mind, these are 5 years old.
One more side-note, there is now a Public Terrarium Server Available.