Spent a lot of time reading this old thread: http://forum.jeelabs.net/node/110fdb0.html?page=1
and was able to find some working code for decoding the La Crosse IT+ 868/915Mhz sensors.
Tested the code with my 915Mhz sensors and it seems to basically work (although it doesn't
seem to completely decode the messages from my sensor).  So this should be a good starting point
for the rest of my development.