Scott blogged about mutli-core builds using MSBuild from the command line, as well as a "hack" from within Visual Studio. I followed the instructions as outlined in the 2nd post and it seems to work for the most part. The solution I was trying it on was fairly small and contained a mix of Compact (CF) and Full (FF) framework projects which seem to cause some issues.

As pointed out in the 2nd post, you are not going to see much advantage to multi-core builds for small projects. I will probably revisit this when my project gets allot larger, as well as look into build configurations and targets (custom MSBuild Files) for my CF/FF project mix.