I've just posted three brand new Office Live Screencasts. Albert Shen, a software design engineer on the Office Live team recorded them and did a fantastic job showing how to use SharePoint Designer 2007 to customize the Office Live environment.
Here are direct links to the screencasts:
1. Office Live with SharePoint Designer
2. Using the Data Form Web part in Office Live
3. Office Live Workflows
By the way - the Office+Live tag on Channel 9 gets you to all the latest Office Live content.
These are good ones!