Using Visual Studio Shell as a starting point and Mono as a runtime, Embarcadero Technologies has introduced a new version of Delphi for .NET called Delphi Prism. This project is being target towards cross-platform developers who want to bring the .NET ecosystem with them to OS X.
The IDE "Add-on Studio for World of Warcraft" was developed in roughly two weeks by two developers using VS Shell as a base. It features Intellisense, tool panes, and a graphical design surface.
A new version of the Microsoft Visual Studio 2008 SDK preview has been released. Among the new samples is a way to add WPF support to a .NET language.
For a number of years Visual Studio has supported non-Microsoft languages as plug-ins. However, the high cost of Visual Studio itself prevented it from being a platform for 3rd party language developers. This has changed with the announcement of Visual Studio 2008 Shell.