Porta Portal and Delicious both appear to hold great promise: Porta Portal as a repository for web sites with strong ties to class room content and Delicious as a tool to extend the search for those sites.
Still thinking about the architecture. A website might be the correct entry point for the "digital environment" to be created. The website could have pages dedicated to each course. These pages would then provide a repository for all the digital materials associated with a course. The website would also provide a launching point for each class and the materials, blogs, wikis, etc of that particular class.
Hmmm. When do we start classes?