Mercury - The Amazing Liquid Metal

I opened a thermometer, not realizing that it was broken and the glass and mercury fell on my counter. I cleaned up the glass but left the mercury. The boyz had a blast poking and moving the amazing liquid metal around with a plastic spoon.
I really miss having internet access in our home at times like these. The kids want to know more about this unusual substance. At what temperature does it become a solid like the common metals around us? Where is it found? What is it used for?
I remember holding mercury in my hand and playing with it in science class when I was a girl. That was really neat!
I heard that they call HAZMAT or something when people are exposed to mercury now. I hope that is an exaggeration! I did not let the children touch it with their skin (or eat it or smell it...now I'm just being silly) just in case.