Drag and Drop: Several elements on the page can be dragged around the screen and positioned wherever you want them. This is thanks to a javascript add-on from Walter Zorn available at this link.
Sortable Drag and Drop: The actual drag-and-drop columns used in the exercises are thanks to a script originally by Tim Taylor, more information here and here.
Fade-In/Out Effects: The fade-in, fade-out functions for the tips, etc, were taken from this site -- it provides one of the nicest effects I've seen and appears to be completely cross-browser compatible.
Multiple Choice Quiz: Finally, the multiple choice quiz used in exercise was take from CJ Website Design, which you can download here.
So, a lot of this part of the site is like a Lego project -- just putting the pieces together. It is a work in progress, and there may be some minor mistakes in it. If you find some, let me know by clicking here
The quizes are primarily for the benefit of my daughter, who is learning German.
Also, if you're interested in working together to create these sorts of quizes for German/English, let me know.
Finally, if anybody knows of a really good JavaScript book they can recommend, please let me know. Most of the ones I've picked up spend way too much time on HTML and/or CSS.