BuildProject.proj

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003"
         ToolsVersion="4.0"  >

  <ItemGroup>
    <DeployFiles Include="..\Output\**\*.*" />    
  </ItemGroup>
  
  <Target Name="Deploy" DependsOnTargets="_Clean">
	<!-- For now Output folder does not even existis -->
	<!-- MSBuild will build all stuff an put to Output folder -->
    <MSBuild Projects="@(ProjectFiles)" Targets="Build" Properties="TrackFileAccess=False;PublishRootPath=..\..\Output;"/>       
    <!-- Now lets do something with DeployFiles files -->
	<!-- In MSBUILD 3.5 it will be empty -->
	<!-- In 4.0 it will behave as expected -->
    <Copy SourceFiles="@(DeployFiles)" DestinationFiles="@(DeployFiles->'$(DeployPath)\%(RecursiveDir)%(Filename)%(Extension)')" /> 
  </Target>

</Project>