The SHT1x series is not I2C, but the protocol is well documented and straight forward. My weather projects are PIC based, so I can't provide the Wiring code for the Ardiuno. However, a quick Google turned up several hits and this hit
seems to indicate that the problem has been solved. Perhaps an email to the author would be worthwhile. Your other option is to take some sample code for the PICAXE, Stamp, or other processor, and port it to the Ardiuno. It wouldn't be too hard to do based on my past experience with the device.