If you are migrating to VS.NET 2005 and converting projects, the VS.NET conversion wizard will do that for you. Then you can use MSBee to compile into both 1.1 and 2.0 assemblies.

However, if you are migrating the build process perhaps before all projects in your organization have migrated, people will still be developing in VS.NET 2003 for some time, yet you want to have a standardized build process, around MSBuild.

This little MSBuild task will convert a VS.NET 2003 project on the fly so that you can use MSBuild to compile it.

Pretty niche scenario, yet since I found myself there, others probably will too.

It is easy to use, you just slap a Using element and then use the task, giving it the projects name. Thats it. Installation is xcopy. The readme gives step-by-step instructions. Happy building!