Installing Oracle 11g on Ubuntu 11.10
AskUbuntu.com has this question: How to install Oracle 11g?.  

Oracle Database 11g and Ubuntu 11.10 Oneiric Ocelot has some good information.

Here are some obligatory links to the relevant 11g pdf documentation.


Database Installation Guide for Linux
Database Quick Installation Guide for Linux x86
Database Quick Installation Guide for Linux x86-64
Release Notes for Linux