From my webcast today - here are the links - be sure to search using the tags 'MOSS' and 'SharePoint' on my blog for even more information!
Link to Developer Introduction to Workflows for Windows SharePoint Services 3.0 and SharePoint Server 2007
downloads for development environment
WSS 3.0 SDK
Sharepoint 3.0 SDK
Nick Swan's Blog re-workflow in MOSS
Paul Andrew's Blog - workflow general
Eilene Hao's webcast - workflow development in VS for MOSS