The SHT3x series is the most recent RH/temperature sensor from Sensirion, one they have said will stick around for a while. I put together a demo, attached for the BS2pe. It is rudimentary, simply acquires and displays the readings as they come in as raw data and also converted to engineering units. The SHT31 is nice for the Stamp, because it runs fine on 5 volt power. Also, the math is easy, linear, with no need for temperature or voltage compensation.
Also attached is a demo for the previous generation, SHT21 and SHT25, which wants 3.3V power .