Brice Dunwoodie has written a nice article on CMS Wire about the latest release of the SmartPart (aka the Return of the SmartPart).
Easy Web User Controls for SharePoint (MOSS) 2007
SmartPart v3, also known as the “SmartPart for SharePoint 2007” has been released. This is a container WebPart that can host any ASP.NET 2.0 Web User Control (ASCX). If you ever needed an excuse to get started with MOSS development, this is certainly it.
The SmartPart module is an open source WebPart for SharePoint that can host any ASP.NET Web User Control. For single file controls, control deployment is very simple. For more complex controls utilizing code-behind files and assemblies, additional configuration is required.
For those familiar with WebPart development, you know there are some challenges involved. For starters, there is a fair bit of code required and there is no design-time support for WebParts in Visual Studio. These are both substantial issues.
SmartPart addresses both of these issues by allowing developers to code simple (or complex) Web User Controls (.ascx files) utilizing the full set of visual development tools in VS and then deploy the result to a SharePoint (MOSS) 2007 site. (read full article)