The temperature, humdity and wind sensors are from Oregon Scientific. I then use a receiver from RFXCOM which receives the RF transmissions from the Oregon Scientific receivers and makes them available via Ethernet.
The data is read from the RFXCOM device using the xpl-rfxcom-rx script from xPL Perl.
The server room temperature sensing device is a Maxim DS18S20 IC. There are a number of similar chips in Maxim's 1-Wire line.
The sensor is mounted in a generic 2 port telephone jack from Radio Shack. Inside the jack connect pins 1,3 from the sensor to the red wire from the right port and the green wire from the left port. Connect pin 2 to the green wire from the right port and the red wire from the left port. On the outside of the jack label the right port as "in" and the left port as "out". This allows you to chain the sensors. Starting from the serial port adapter, you connect a phone cable to the "in" port on the first jack, then connect a phone cable from the "out" port on the first jack to the "in" port on the second jack, etc.
The telephone jack is then connected to a DS9097 1-Wire serial adapter using a standard phone cable. (You should probably get the newer DS9097U adapter.)
It should be noted that I entirely cribbed this design from some nearly identical devices that Lee Damon rigged up for our server rooms when we worked together.
The temperature is read using DigiTemp.
The UPSs are APC SmartUPSs which have internal temperature sensors. The temperatures are read using the apcaccess program from apcupsd.
The data is stored in an RRDtool database. The graphs are also generated by RRDtool.