For weather stations, my recommendations are as follows:
1. Nielsen-Kellerman Company -
Kestrel 4000 Pocket Weather Tracker - it can be also connected to your PC or laptop
http://www.ambientweather.com/ke40hawestgr.html
http://www.ambientweather.com/ke40coin.html
2. Davis Instruments -
Perception II - great weather station and widely used by many racers.
http://www.davisnet.com/weather/prod...asp?pnum=07400
http://www.davisnet.com/product_docu.../apnote_14.pdf
For software, I use Patrick Hale's Density program.
http://www.quarterjr.com/density.htm