I needed a thermometer for my bike this and picked up this one from ebay:
It works surprisingly well. I compared it to my precision mercury thermometer and it's accurate to within 1 degree. The unit looks waterproof although I haven't tested that yet. The sensor is on a lead so I can hide it from the sun. It only cost me $11.50 with shipping. It only comes in Celsius though so I have to do a quick conversion in my head and the display is hard to read in sunlight. It needs some kind of shade.
I thought I'd mention it since it took me a while before finding a thermometer I liked.