I just stumbled upon this site. Very cool stuff.
I built out a monitoring system a couple years ago using (used - cheaper that way) shipping scales with serial output. I have a larger one that will hold a 1/2 barrel but usually use 3 1/6 barrels.
For temperature monitoring I used phidgets.
The code is all Java on the back end. Also a Facebook app to display the results on your profile. And a Flex GUI to talk to you when you pour a beer or yell at you when you leave the kegerator open too long.
If anyone is interested in knowing more, let me know.