MSBee means MSBuild Everett Environment. Everett beeing the codename for .NET 1.1, MSBee is an extension for MSBuild that allows developers to build managed applications in Visual Studio 2005 that target .NET 1.1.
A small limitation to know though: "At this time, we are not planning to add IDE support. Since MSBee will be a shared source release, the potential is there for the community to provide this support.".
Update: Bruno Baia made the test, and yes, you can compile directly from VS 2005 if you add the following line after the existing import tag in a project file:
<Import Project="$(MSBuildExtensionsPath)\MSBee\MSBuildExtras.FX1_1.CSharp.targets" />
IntelliSense and help still present .NET 2.0 information, but this is not a big deal. I think the above statement about the missing IDE support is not clear at all.