As my company migrates towards the .NET framework from VB6, it looks like we are going in the direction of WPF (my boss is in love with the Office-style Ribbon control). I've been working to mock one of our VB6 applications in WPF and decided to experiment with MVVM at the same time. I'm being discouraged from using an existing MVVM framework, so I guess I need to write my own. The biggest concern right now seems to be a method for registering and managing all my views from a central spot - a manager class - but I'm not exactly sure how to implement this. I see article on IoC and ServiceLocator but have a are time putting those ideas to use. 

Does anyone have suggestions on the features and patterns that I should be implementing to make a very lightweight, but serviceable MVVM framework? Aside from an existing framework, what existing code resources would you use to help progress this a project like this?