If you get an error like the following on your build server:
error MSB4019: The imported project “C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v9.0\WebApplications\Microsoft.WebApplication.targets” was not found. Confirm that the path in the declaration is correct, and that the file exists on disk.
You have two options. You could copy Microsoft.WebApplication.targets from your development box, or you could install Visual Studio on the build server. The simplest solution is to copy the file, making sure to reproduce the directory structure exactly.