Download Installer Programs
In order to automate the creation of installers as much as possible you need the write software for creating installers. You want an installer program that creates installers based on text files or that can be automated through the use of a command line tool or AppleScript.
Here are suggestions for programs that I use on Windows and OS X. Download and install these programs if you would like to test building installers.
Download INNO Installer For Windows
INNO Setup is a free installer for Windows programs. You write scripts that are then compiled into installers. Because the scripts are text based the framework can automate the creation of them.
Download FileStorm Demo
An Apple-scriptable Disk Image Creator which means the DMG creation process can be completely automated on OS X.