The two ways I know are:
a) tap locks, which are spendy and from reports don't work all that well, (if you pull, they still dispense)
b) put a lock on fridge, and pop off liquid lines each time you finish pouring a beer, (which seems like a helluva lot of work).
I figured this could help some people.
First, lock your kegerator so no one can get into it. A padlock and simple latch from Home Depot will do the trick.
Second, get yourself an ignition switch. I found this one on Ebay for just a few bucks: http://cgi.ebay.com/ebaymotors/Ignit...#ht_4032wt_912
Then, grab one of these for each tap you have, and install it in the beer line:
It's a 12 VDC solenoid activated valve with 1/4" NPT fittings. Attach a few barbs to it and install it inline on each beer line. These run $20 each, but that's no more than the cost of the tap locks.
Finally, grab a 12 VDC power supply....this one is 4 amps, meant for a laptop, and runs only $13, and will run 8 of those valves.
Way I figure it,you install a valve in each beer line, connect them in series parallel
(thanks sawdustguy) to the laptop power supply and the ignition switch, and install the ignition switch on the outside of the fridge.
When you want a beer, insert your key and turn the ignition on. All the valves open up, and all the taps are live. When you have your pours, turn off the ignition and pull your key, and all the taps go dead. Easy Peasy. What do you guys think?