Footnote Links Module
The Footnote Links module for Drupal has a content filter which turns inline links (such as in a blog post) into footnotes. The idea is to allow a reader to concentrate on a piece of content, but to also allow for the person writing the content to do so more easily.
Drag and Drop Form Builder
I created a proof of concept drag and drop form builder. It allows a users to select form elements and drag them together to create a single HTML form.
Zombie Simulator
The zombie simulator simulates a zombie apocalypse scenario using geographic databases (in this case PostGIS). It allows for the creation of zombies (random point data), calculating how many zombies there are in an area (point density) and finding the distance to the nearest zombie. The zombie simulator is implemeneted as a Drupal module.