Just a quick recap and aggregation of links I used to set up a VMware virtual machine running Ubuntu 6.06 with Apache 2.2, Mongrel and Ruby on Rails. These links don't discuss creating a virtual machine and assume it's already set up and has internet connectivity.
1. Follow first 7 steps given in the How-To here.
2. Install and set up the Apache, Ruby, Mongrel and MySQL pieces based on this post.
One item not discussed is how to set up Apache so that it starts up automatically when the system is booted. Here's how:
First create a symbolic link to the apachectl file:
ln -s /usr/local/apache2/bin/apachectl /etc/init.d/httpd
Then this Debian magic:
/usr/sbin/update-rc.d httpd default
3. Configuration and finish here.