I was hoping that Microsoft would address the need to target earlier versions of Visual Studio within the Visual Studio 2010 IDE, but since they decided to punt, I tackled the problem myself. I’ve released my solution as an open source project named Daffodil for Visual Studio.
With Daffodil installed on your system along with earlier versions of Visual Studio, you can use the new native multi-targeting feature in Visual Studio 2010 to target those earlier versions. This makes it possible to use Visual Studio 2010 for building ObjectARX projects, for example. Daffodil performs essentially the same function that my VC Build Hook utility did in Visual Studio 2008 and 2005.