Good question.

If you work extensively with Visual Studio IDE, you most likely have created some Macros and Add-ins to speed things up.  Why not share that with others (but not your manager, otherwise they might assign you more work), you can show off your skills, etc.

Take a look at Introducing the Visual Studio SDK, here you can find out more about how you could:

  • Add commands, windows, and other features to the IDE.

  • Extend the Visual Studio editor.

  • Enable support for a new language.

  • Extend data designer functionality to external data sources.

  • Add your own project-type templates.

  • Integrate custom source control.

  • Customize the Visual Studio debugger or create your own.

  • Create and manage your team test suites.

You can use one of your favorite languages as long as your favorite language is: C#, VB, VC++ to create the extensions.  I have not tested F# yet and the documentation doesn’t mention it.