"The SmartPart is a generic webpart that can contain an ASP.NET user control. Nothing new you would say, but the SmartPart can give your user control access to the SharePoint object model. So from within the code of the User Control you can do stuff with SharePoint! Another feature is that the user control can expose some properties which the SmartPart picks up, so the user can specify values for these properties in the SharePoint site. To prove you how easy it is, I’ve create a small demo. In this demo I will create a DropDownNavigation webpart in less than 5 minutes (it could be less, but I made some typos). The webpart will show a dropdown list in which the subsites of a SharePoint site are displayed. When a site is selected from the list, the user will be redirected to that site. Here’s the video. "
Jan Tielens’ Bloggings : Introducing "SmartPart for SharePoint"