Just recently I made home made play dough to hand out in my son's class. But now that I think about it, after reading the reply above mine, I hope no one drops theirs and accidentally cuts themselves. I put little fabrics on the top with yarn to tie them on and a note telling them to make a Christmas ornament out of it and let it dry. Voila.
I just saw how to decomposh tissue paper or napkins onto the jar and put a tea light into it for gifts. (Which is what I'm doing for my extended family. I can't afford to buy Christmas gift for my extended family this year so I figured hey I got tons of jars and tissue paper. Plus it's great for those jars you've lost the lids to.)
With the left over lids I saw this website can't find it now, but it made magnets with the left over lids. It was a lady bug made out of felt and a magnet glued on the back.
And there was a website that talked about making the jars into herb holders, and pin cushions. Oh and the lids they made into a Potpourri magnets. They had lace covering the Potpourri and a magnet on the back: http://www.seedsofknowledge.com/babyjars.html
With this website it shows how to make a fish bowl effect with the jars: How cute huh? I mean you can buy those confetti looking fishes to put in the jars. http://rivalpro.net/~craftykid/babyfoodjars/index.shtml
Boy now your getting me excited on making more crafts with the jars than what I was originally was going do for my extended family. Ha, HA! Hope this help!