Update
(March 2006): With Oracle Database XE in production, it is even easier
to install Oracle on Debian-based distros (thanks to Joel Becker).
There is now an apt-get repository up on oss.oracle.com for XE. Just add:
deb unstable main non-free
to /etc/apt/sources.list and then:
# wget -O- | sudo apt-key add -
# apt-get update
# apt-get install oracle-xe
'libaio' and 'bc' are in the repository, so dependancies will pull them
in if the user doesn't have them. (Note: You will need to 'sudo' or have
'root' privileges to install XE.)