I’ve been playing around with a new MOSS 2007 feature called the Business Data Catalog on which I will give a presentation on friday (blog post will come). One of the biggest challanges was to create a working definition XML file.. using the xsd and of course the Office Server SDK finally made me integrate Tam Tam data into SharePoint, using it in lists and the search center (whohoo!). Screenshots will follow! 
In my opinion it is one of the best improvements in the new version and I see lots of opportunities for our customers and ourselves.
Lawrence pointed on his blog to some interesting resources for BDC development to help writing the definition files:
Database Metadata Generator for the Business Data Catalog
The database metadata generator creates one system and one entity that corresponds to a table or view. Specifically, it generates:
- An LobSystem
- An LobSystemInstance
- An Entity
- A Finder method of the form "SELECT * FROM Table"
- A SpecificFinder method of the form "SELECT * FROM Table WHERE IdentifierColumn = @IdentifierColumn"
Business Data Catalog samplesThis GotDotNet project is dedicated to using the BDC within MOSS and will provide Application Definitions samples for many common LOB systems.