I had one of these and it worked very well for weekends for 3 cats: http://www.smarthome.com/6100/Ani-Ma...-Feeder/p.aspx It is the cat mate c50.

It is still in the cellar; I messed up the timer on it and haven't had time to sit and readjust it myself (yes, it can be done). It also has a place for an ice pack. Here is a demo:
http://www.youtube.com/watch?v=Cn6PUDDKW90