Tucson Amature Packet Radio
This is the fount of all knowledge when it comes to doing digital commumications over amateur radio frequencies. The area of particular interest is the "APRS and GPS" section.
The iButton home page
This is the home page for all the Dallas Semiconductor iButton stuff. They make lots of other things besides weather stations, but on this page is the link to the weather station info. Follow that link to more technical information about the sensor unit than you would ever want to know. There is also the link to order the sensor unit. Especially interesting is the article by Dan Awtrey of Dallas Semiconductor describing the 1-Wire weather unit in detail.
The Freescale microcontroller page
From this link, select 8-bit microcontrollers, then the HC08 tab on the left.
The 6808 Development tools
This is the page for the free development tools for the 6808. They re-arrange the setup frequently, so poke around until you find something that looks like "ICS08GPGTZ" and you should have the right software.