Not only do you see each stage of the knot formation, but you also get a text accompaniment (which you can pause to read) that explains exactly what you need to do at each stage in order to create the knot. This app gave me flashbacks to summer camp, where I learned to tie a bowline with my eyes closed in under 5 seconds ... and that's a good thing.
When my son first saw Animated Knots, he paused for a second and then asked for some rope to play with. I quickly obliged, and he sat contentedly as the app guided him through learning how to tie some basic knots. At our last Denver Apple Geek lunch, Animated Knots got thumbs up from everyone who tried out the app. It is sure to be a hit with any current or ex-Boy Scout, anyone who hunts or fishes, and so forth.
The application is based on material from the website of the same name. I think it has gained something in the translation to app form; I like how easy it is to carry the entire reference around with you and browse through the tree-like navigation structure offered by the interface.
Animated Knots costs US $4.99 at the App Store and is designed for use on the iPhone and iPod touch.