As Scott Hanselman points out in his blog fully, you can take advantage of all your CPU cores when building the solution using MSBuild.

Of course this is a luxury you get if you upgrade to Visual Studio 2008, and is not supported in older versions. Fortunately, since MSBuild in VS.NET 2008 (and the IDE itself) supports multitargetting, if you’re still using .NET Framework 2.0 you can upgrade to VS.NET 2008 and benefit from this feature.

One thing to know before expecting faster build speeds, is to know the dependency tree of your Solution. If your projects are dependent on one another, you won’t benefit much.

Scott also shows a hack to Visual Studio .NET to enable this feature when building solutions inside the IDE.