Sharepoint and WebPart links

Microsoft Windows SharePoint Services (Book) : Chapter 19: Beginning Web Part Development
http://msdn.microsoft.com/library/en-us/odc_sppt2003_bk/html/WSSInsideOutCh19.asp

Best Practices for Developing Web Parts for SharePoint Products and Technologies
http://msdn.microsoft.com/library/en-us/odc_sp2003_ta/html/ODC_WSSWebPartTips.asp