willnue:
Decoding data of Oregon Scientific radio frequency sensors...
http://alyer.frihost.net/thn128decoding.htm
It's the best way to start. I wrote a decoder several months ago and used the wave like the one displayed in figure 1 to interpret 1's and 0's.
Then I made a small change in temperature and looked at the wave again to guess where in the stream the data is stored. The protocol I decoded was totaly different from the one Oregon Scientific uses.
Until I saw that page, I wasted a lot of time trying to read the radio receiver and writing the state to serial.