It keeps getting better. I just saw that we have posted a new version of the SharePoint SDK. I have just downloaded it and will take a look at it. From the site it says that it has some new information about

"This SDK also includes new documentation for the Web Part Page Services Component (WPSC), which is a client-side component that adds dynamic capabilities to your Web Part Page by providing Web Part discovery, notification, and state management services used by Web Parts; and for Windows SharePoint Services RPC methods."

Download the SDK

7:49:39 PM