WebMaker / Kennisnet
WebMaker is a web application that lets you easily create websites. This application targets school children in particular.
Onno worked on this project for a couple of months at Kennisnet. He helped out other developers by sharing his Tapestry knowledge and he worked on several major parts of the application, like the WYSIWYG HTML editing page, the Theme-selection screen with client-side real-time previewing and the Gallery pages to name but a few.