Debian installs a base system with the minimum it needs to run, and then gives you the opportunity to pick sets of packages in tasksel, much like Red Hat (but Red Hat's set sizes are much larger).
You probably want to install Woody with the "bf24" option at the initial prompt. That will give you a 2.4.18 kernel.
For OpenACS you will want some new versions of PostgreSQL and Tcl. For PostgreSQL you want Oliver Elphick's PG packages (he's the mainainer). Add this to your /etc/apt/sources.list:
deb http://people.debian.org/~elphick/debian stable main contrib non-free
For Tcl8.4, you want backports.org's packages. Add this to your sources.list:
deb http://www.backports.org/debian stable tcl8.4
backports.org is a valuable resource. Look through http://www.backports.org/debian/dists/stable/ and just append whatever packages you'd like to the line above, after tcl8.4.
Besides tcl8.4 and PostgreSQL, you need AOLserver too. Francesce Lovergine is Debian's AOLserver 3.x maintainer. He (and several others including I in parallel efforts apparently) have been working on AOLserver 4 packages. Hopefully these will converge.
He has made some AOLserver 4 packages available for unstable on his repository: http://people.debian.org/~frankie/debian/sid/experimental/aolserver/
IIRC David Welton made packages of modules. I don't know where they are. I don't think either of these have woody backports yet. I also made AOLserver 4 packages, but I have to find where in my backups they are (hard drive failure in december).
Francesco, David, how about we join forces on these Debian packages? We'll probably get better outcome. I have a woody machine we can use to build backports (it uses tcl8.4 from backports.org)
Besides these, you'll need tDOM and a fow of the AOLserver 4 modules, which you'll likely have o compile by hand for now. You'll also need ssh and some decent editor besides nano-tiny, the default in Debian's install. vim or emacs21 or your choice.
Make sure you edit /etc/inetd.conf and comment any services you don't need. You can't uninstall portmap, but you can not start it at boot. See the update-rc.d man page.
Debian is an excellent distribution, specially for servers. For desktops you pretty much have to go with unstable (which really is pretty stable).