I usually work in an environment where there are six or more related applications and MSIs.
I have a directory called c:\Deploys, and in that I have a .cmd filed called "GatherMSIs.cmd".
It just has bunch of copy statements:
xcopy c:\Source\FRB\EC\Common\BizTalk\FRB.EC.Common.BizTalk.Deployment\bin\Debug\FRB.EC.Common-1.0.0.msi /Y
Today, I also built for the first time an MSI builder .cmd file to recreate all the MSIs. I just put in a list of statement like this (I did a deploy from within Visual Studio and then just copied the syntax).
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\MSBuild.exe "C:\Source\FRB\EC\Common\BizTalk\FRB.EC.Common.BizTalk.Deployment\FRB.EC.Common.BizTalk.Deployment.btdfproj" /nologo /t:Installer /p:Configuration=Debug