Or, you may download the file.
While most people getting started on Rails will probably be running it on a desktop of some kind, many of them will eventually need to install it on a server as well. (Some brave souls would rather do everything from a terminal window anyway, so this may be a first choice for them.)
If you'd like to develop Rails applications on Ubuntu server, the installation is fairly similar to that for Ubuntu's desktop version, except that instead of a GUI installer you just use apt-get from the command line. It's a similar set of packages to install. For testing the installation, this demonstration uses lynx, the seemingly timeless text-based web browser.
This screencast takes you through the installation steps of Chapter 1 of Learning Rails, but focuses much more tightly on Ubuntu. While it's a server installation, though, it's not really a deployment. The tools installed here are enough for development, but aren't meant for exposing appliations to real-world traffic. A later screencast will cover deploying Phusion Passenger, as described in Chapter 18 of Learning Rails.
Update: If you're curious about the distinction between deploying software with apt-get and deploying with ruby gems, you might find this strongly-opinionated discussion interesting.
For more screencasts and information about Rails and Learning Rails, see Excursions on Rails.