MSDN
We previously posted a tip sheet on Getting Started with SharePoint WebParts. Kindly supporting us in these endeavors, our dear friends over at MSDN have published a chapter from the book Microsoft Windows SharePoint Services Inside Out.The chapter, Beginning Web Part Development, covers the following topics: * Configuring Your Development Environment * How Web Parts Work * Starting a New Web Part Project * Writing Web Part Output * Adding Layout Controls and Content * Manipulating SharePoint Objects * Using the ASP.NET Event Model * Exposing Custom Properties * Using Web Part Tool Parts * Providing a Design Time HTML Provider * Assigning a Strong Name * Deploying Custom Web Parts Its an excellent resource for first time WebPart developers.