Popular and cheap sensors for that purpose are also DHT11 and DHT22 which are temp/hygro sensors, I've interfaced the DHT11 to a couple of projects, however the datasheet for the DHT22 has errors preventing me from getting it to work.
Its a non standard serial interface that can only be accesed really by some kind of processor.
I suggest if you want to do something without having to program a chip that you use a resistive or capacitive humid sensor, philips do a couple and a linear temp sensor such as a LM35 which has a voltage output.