[Blog Map] This blog is inactive. New blog: EricWhite.com/blog
I've written an MSDN article, Using the SharePoint 2010 Managed Client Object Model, that provides the basics on using the Client Object Model. Many thanks to Michael Cheng of the client object model team for technically reviewing the article, and providing me with many suggestions that improved it.
The article Using the SharePoint 2010 Client Object Model with the Open XML SDK 2.0 provides additional information around uploading and downloading files from a document library, as well as examples that modify Open XML documents using the Open XML SDK.