Knowing how to make things with conic sections is a very useful skill. I've always wanted to do it, but I couldn't find a description of how to do it that made sense to me.

Now, finally, I found it. Naturally it's on www.fiddlersgreen.net, the inordinately cool card modeling site. Nearly every model on fiddlers green has some sort of conic section in it somewhere, and they now have a nice little set of tutorials on how to develop shapes out of cones, take a look! My personal recomendation is the designing without cad one.