Can't resist posting this. On successive days I saw a squirrel and a feral cat getting water by licking ice in our backyard. To provide a source of drinking water for all the assorted wildlife living out there or passing through, I built this heated water bowl.
A thin-film heater that I got as a trade show sample years ago and a TMP 37 temperature sensor are attached to the underside of a small, cheap stainless steel pet food bowl using Kapton tape.
A Duemilanove reads the sensor on A0, controls the 6.7 volts to the heater using an FET driven by D3, really all I changed in Brett Beauregard's excellent PID library sample code was the math to change from TMP 36 to TMP 37.
Water consumption and tracks found in snow indicate that a source of liquid water in midwinter is becoming very popular.