In scouts we do a lot of knot tying. The downside of this is that the parents usually have to learn them first! I don't know about you, but squinting at a lot of knot diagrams just doesn't always help. That's why this site, animatedknots.com, can be a huge help. Alternately, Boy's Life magazine has some knot videos online for the more common knots.
Knots have a lot of good uses and are a great way of building motor skills.