If you're into that kind of thing, Eli says there's a free book download about SharePoint 2007. Download the PDF directly from here.
Eli says:
"Future or current SharePoint developers should at least flip through the book to build a picture of how MOSS 2007 fits together and what the concepts are -- changes to the security model, site definitions, site features, Content Types, how Workflow is integrated, Excel Services -- there are a hundred small topics, you owe it to yourself to get a handle on the big picture. "