At TechEd, we made some important announcements such as the naming of the next version of Visual Studio (Visual Studio 2008 - formerly Visual Studio Codenamed "Orcas") and SQL Server 2008 (formerly Codenamed "Katmai"). Another announcement we made was the Visual Studio 2008 Shell, an environment where you can host your custom tools and even new programming languages. The cool thing is that you can brand Visual Studio as a custom application!
There is two ways you can "hook" into Visual Studio - integrated mode and isolated mode. Integrated mode allows you to build a version of Visual Studio which will merge seamlessly with other editions of Visual Studio installed on the same machine. If you are familiar with Team System, you've already seen this kind of functionality whereas if you install Team Edition for Software Architects, Team Edition for Software Developers and Team Edition for Software Testers on the same box, you end up with Team Suite. In other words, it's "additive" - your functionality can plug in and play nicely side by side with the core features of Visual Studio. A lot of our tools were built using a shell similar to Visual Studio, such as the SQL Server Management Studio which shipped with SQL Server 2005. Think about the tools you build in-house and how cool it would be to have them integrated in Visual Studio, instead of running them as separate disconnected apps.
The second mode available in the Visual Studio 2008 Shell is isolated mode. Using isolated mode, you can build a standalone application with the Visual Studio shell which will run side-by-side with your existing installed version of Visual Studio. If you are building an IDE type of application, does it make more sense starting from scratch or using Visual Studio at the base? You can incorporate custom explorers (like the Solution Explorer), designers, editors, toolboxes and menu items. If building a custom designer sounds like a project you would like to do, I'd recommend you check out the Domain Specifc Language Tools (or DSL Tools) that enable you to build custom graphical designers and generate source code from your designs.
The next logical question is "how do I get it"? The Visual Studio Shell will be freely available as part of the Visual Studio SDK starting with the release of Visual Studio 2008. Building and deploying applications based on the Visual Studio Shell will be royalty-free. You can learn more about the Visual Studio 2008 Shell here.