This wiki has been moved to https://github.com/SuperTux/wiki into the mediawiki branch.
If you have created your own levels, and wish to release them, then you can place a link here. Alternately, follow the guide at Contributing if you want them to be in the main game.
The development version has the ability to automatically download some specially packaged levels, known as "addons". Simply ensure you have an internet connection, and select "Addons" from the main menu, where you can choose to install the 3 addons currently available.
In the SVN version, there is a special island, Incubator Island. In this world are brand new levels that we plan to include in the main level set once they are "ready", i.e. well tested and fun to play. You can actually help us by playing those levels and giving us feedback about them.