I was on a machine with no dev tools and needed to recompile a .dll for .NET 1.1.  I had the .csproj file and am so MSBuild-centric that I figured I'd open a command prompt and type:

set path=%path%;%windir%\Microsoft.NET\Framework\v2.0.50727

Then I'd be all set.  Ah, but I forget that this was a .NET 1.1 project -- no love.  Fortunately, the good folks from Visual Studio created a "power toy" (gotta love power toys) that allows you to use MSBuild to target .NET 1.1.  It is called MSBee.

Once that was installed (which required I download the .NET 1.1 SDK, kind of large at 100+ MB but what can you do?) I was able to compile the assembly.  Their docs were a little confusing; they suggest you can either add an <Import> to the .csproj file or pass some switches to MSBuild. I had to do both, adding the <Import> statement:

<Import Project="$(MSBuildExtensionsPath)\MSBee\MSBuildExtras.FX1_1.CSharp.targets" Condition=" '$(BuildingInsideVisualStudio)' '' AND '$(TargetFX1_1)''true'" />

As well as passing the following switch:

msbuild [project file] /p:TargetFX1_1=true

But once I did that I was good to go!