When I build a solution on my build server it generates a binaries folder and then later on copies these binaries to the final output folder. In my case some of the third party
For ASP.NET projects there is a built in mechanism for this. Ensure required assemblies are in a folder under your project named _bin_deployableAssemblies and they will get automatically copied. To see how this customization is wired into the build of Web projects, find the file...
%PROGRAMFILES%\MSBuild\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets
And take a look at the _CopyBinDeployableAssemblies target. In that same file you can see it referenced like this...
$(PrepareForRunDependsOn);
CopySilverlightApplications;
_CopyBinDeployableAssemblies;
...
You can do a similar customization on any project, since the target PrepareForRun is part of the common MSBuild targets in Visual Studio.