So you just went to the big box home improvement store, bought a new programmable thermostat, installed it yourself. Only had to call the help line once, used less swear words than the kids swing set project and you can’t wait to see your next electric bill. Good Job! Helping to save the environment.
But wait! Don’t break the law. You can’t just throw your old mercury-containing thermostat in the trash or recycle bin. Even if it is not illegal in your state, please be environmentally responsible. When these thermostats are dumped into landfills the mercury glass bulbs become broken. Mercury then seeps into the ground water contaminating the underground aquifers which flow to creeks, rivers, and lakes and even sometimes become drinking water causing health problems for humans, fish and other wildlife. 
To find a drop off site in the U.S.
To find a drop off site in Canada
WWW.switchthestat.ca/eng/dropoff.php/
Pictures courtsey of Google Images.