Good points retrolefty. I am trying to "do it right" from the get go with this project, but I guess there comes a point where it becomes hard to impossible to get the kind of accuracy I want. Still, I want to do whatever I can to ensure the accuracy is as good as possible with this type of setup. In case anyone else is interested in this type of project I'll try and keep updating here as I progress.
I have ordered the uno r3, should be here by the end of the week. That should at least give me something to start testing and messing around with. In the meantime, I've been doing some more research, and have not been able to find a decent (at least 0.1c) integrated humidity/temp sensor package yet. Therefore, I've been seeing if a separate thermistor/humidity sensor approach would work, and it seems that humidity sensors need to take the current temperature into account when performing the RH% calculation. If using separate sensors, this could lead to some calibration nightmares that might not be there with integrated packages. In addition, I have not found a very easy, straightforward way to read capacitive humidity sensors with the arduino, still searching around but so far it seems pretty complicated and something which would require its own circuit. Basically the capacitive sensors seem to require an AC waveform of usually 1khz or higher in the reading process. I'm still quite green to this stuff so it's proving a bit much so far. I did however find this somewhat helpful thread:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1264143673
Another issue I've come across is calibration for the thermistor. The 0c ice bath part is probably do-able, but good calibration will also need data gathered at exactly 25c and a third point (like 100c) as well. I don't see any easy way to calibrate those other points without expensive calibration equipment which I don't have. 100c is outside the range of most thermistors as well, so sticking one in boiling water will ruin it in that case. Still trying to figure out more info on this part.