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SpicIE is a
framework which allows you easily to extend Internet Explorer 7/8 with your own plugins. SpicIE wraps/hides the IE COM extension interfaces and makes it easy to develop browser extensions in managed programming languages.
SpicIE is designed for simplicity. The initial creation of an Internet Explorer plugin with SpicIE takes only minutes until you have a runnable, debuggable code base which you can extend with your own functionality. There are lot of scenarios where browser plugins could be useful. SpicIE lets you develop your own browser functionality comfortable with minimal technical efforts.
With SpicIE you can develop your own:
- IE browsing event handlers
- IE toolbar buttons
- IE menu entries
- IE context menu entries
- IE explorer bars
- IE toolbars.
Important: SpiceIE is released independently of Internet Explorer and related products. It is not an officially supported product by the Internet Explorer team. While SpicIE is a valuable tool for prototyping and testing Internet Explorer extensions, it is not recommended for use with released software. SpicIEContrib - SpicIE plug-in samples & guidance
http://archive.msdn.microsoft.com/SpicIEContrib 
SpicIE is designed for managed plugin development. You can develop SpicIE plugins in any managed development language. You will have Visual Studio 2008 project templates for C# and VB.NET plugins.
SpicIE is tested with Internet Explorer 7/8. You can develop SpicIE plugins with all Visual Studio 2008 versions. SpicIE plugins can be executed by .NET 2.0, .NET 3.0, .NET 3.5.
There are some blogs entries about SpicIE at following blog -->
http://blogs.msdn.com/mtcmuc/archive/tags/SpicIE/default.aspx SpicIE is published unter
Microsoft Permissive Limited License.