Are you aware of the
Debian Live Project? They offer customisation scripts at just about every level, but you'll have to dive into it to use them to their full potential. The installer's the standard
Debian installer, though - not just point and click, then (even if the new
Lenny installer's a lot nicer to look at).
gNewSense also offers scripts to fully customise a
gNewSense or
Ubuntu based distro - I'm not sure if it'll work for
Debian, too.
Finally,
Debris Linux has a simple custom installer, and customising an installed version's really a breeze. We may even be able to offer a customised version tailored to your needs if you can give us precise descriptions and requirements of what you need. (Note: Right at this moment, the webserver seems to be down - should be up again in the not-too-distant future).
Edit:
Just found this:
Ubuntu Customization Kit
M.