For installing on multiple computers it's possible to do fully automatic installations. Debian packages intended for this include
fai-quickstart (which can use an install server) and the Debian Installer itself. Have a look at the FAI home page for detailed information.
The Debian Installer supports automating installs via preconfiguration files. A preconfiguration file can be loaded from the network or from removable media, and used to fill in answers to questions asked during the installation process.
Full documentation on preseeding including a working example that you can edit is in Tillegg B, Automating the installation using preseeding.