For more information on SharePoint and Web Parts, please
check out these past posts of mine:
SharePoint
2007 -- Built on ASP.NET 2.0
Office
2007, VS 2005 Tools for Office, and VS 2005 Extensions for SharePoint
Writing Custom Web Parts for SharePoint 2007
Also check out the SmartPart control
plug-in for SharePoint 2007 that allows you to deploy any ASP.NET 2.0 user
control as a web part within SharePoint 2007.