Lua
Lua (moon in Portuguese) is a lightweight, easy to learn, free and very efficient scripting language.
It is widely used in Wikipedia's Mediawiki through the Extension:Scribunto, and we also use it on our web.
Troubleshots
Doesn't work with Mediawiki 1.21, which is the one we use for laussy.org (it works with 1.22 that we use locally).
If a module is not running, it might be because its page is declared as wikitext. To fix that in the info section (say ?title=Module:Quote&action=info for the Quote module) change Page content model to Scribunto module.