While you're away you can let your cats have the run of the place, but if you put out too much food at once, hilarity may not ensue. You can make a pretty easy automatic feeder using a glue stick, cardboard, a continuous-rotation servo and an Arduino.
WonderHowTo's Mad Science weblog shares this project which relies on an earlier glue stick servo linear actuator build. As shown in the video above, an opening for a cat food supply is lowered by the actuator for a few seconds and (ideally) a single meal portion of food will drop into a feed bowl. This is timed by an Arduino, but I imagine you can get the same effect by using a common lamp timer.
Admittedly this might be a bit of overkill, but it seems like a good introduction to Arduino and the glue stick servo looks like a good trick to have in your bag. Other than the Arduino the project is cheap (the servo is $US13 and everything else you probably have on hand) and shouldn't take much time to put together.