Getting started writing web pages using lightweight markup languages can be intimidating to the beginner, or even the expert who hasn't dealt with it before. Many of the LWML pages tell you the syntax of the language (often in excruciating detail), but leave out the basics, like how to even install and run the software.
This is often because the methods to install it are different on different OSes and distributions, and so I've tried to gather enough information here for someone to get started quickly on Ubuntu.
This information is correct for Karmic Koala (Ubuntu 9.10); check /etc/lsb-release if you don't know what version you're using.
This is one of the simpler LWMLs to start to use.
sudo aptitude install python-markdown
markdown_py your_file.md > your_file.html
sudo aptitude install emacs-goodies-el
This one actually a bit baffling, since there's no packages with "ReStructedText" in their name, and once you've installed it, there's no indication of what the name of the executable is!
sudo apt-get install python-docutils
rst2html your_file.rst > your_file.html
Emacs LISP for ReST is already installed on Ubuntu.