Below are configuration notes for setting up various versions of Ubuntu server for hosting Ruby on Rails + MySql apps. Most of the servers that I've configured using these notes had been running on Amazon EC2 instances using the AMIs provided by Ubuntu. There may be slight differences with other Ubuntus.
For my own purposes, I've written these notes in shell script format so I could just copy and paste the relevant parts into the terminal. I generally run each of the commands manually, but I suppose one could theoretically tweak the file so that it could be run as one continuous script. The only hiccup, I think, would be the MySql server installation which requires you to enter a root password.
I only have notes going back to the Meerkat release, as before then, I had been using CentOS for most of my projects. If I find those notes, I'll post them in the notes as well.
Ubuntu configuration for RoR and MySql
Ubuntu 11.04 Natty Nahrwal
Ubuntu 10.10 Maverick Meerkat