I noticed an advertisement for an "ergonomic egg chair" and decided to take a peek. It looks like the same sort of idea as is behind those ball chairs, except instead of sitting on a ball, you're sitting on the tip of an egg. The site that's selling them is http://www.sellcom.com/ergochair.html. The price listed is $198 with free shipping to the continental US. Personally, I'../../2004/06/herman_miller_a.html">Herman Miller Aeron, but if anyone has tried an "egg chair" and would like to leave their comments, I'd like to hear some opinions.