The hardware for my Weather Station are 1-Wire devices from Hobby Boards.
They carry a complete line of 1-Wire devices, many weather related.
The advantage of building a station from these components are cost and flexibility. Each device is relatively inexpensive and you only need purchase the devices you wish. I put together my station for about a third the cost of a comparable Davis Instruments station.
There are many open source software packages for use with 1-Wire devices. I have a Linux server running Ubuntu 7.10 that runs the Weather Station.
Since the 1-Wire devices are attached to my main server via CAT-5 cable the main disadvantage to this setup is that I basically have a lightning rod wired into my PC.
Here is a list of my Station components:
Temperature + Humidity
AAG Wind Instrument
The requirement for the 1-Wire devices to be attached via CAT-5 to my server meant that mounting options were limited. The 1-Wire bus is supposed to be good for over 300 feet but obviously the shorter the better.
I chose to mount the Wind Instrument and Rain Gauge to roof near the end of the house so as to easily run the the CAT-5 to them. I bolted them to a mounting system intended for satellite TV dishes.
I used a COMMDECK RETRO8 mount that easily installs under the roof shingles. Installation was a snap.
AAG Wind Instrument and Rain Gauge mounted to roof.
The capped white tube is 2" PVC used to protect two CAT-5 female-to-female connector blocks from the rain. It's open at the bottom and the blocks are attached to the tube sides with velcro tabs. Keeps the rain out during the worst Texas thunderstorms and still allows easy access if disassembly is required.