I'm gone semi-regularly because I have to travel for work sometimes, and my mum's from Dublin so I go overseas to visit my family. Unless I'm going to be gone for over two weeks, I don't do anything to feed the fish. I just leave them, and I've never ever had a single one die of starvation while I was out of town.
If I'm away for more than two weeks, I will have someone come feed them and do a water change once a week, but unless it's my brother doing the feeding, I pre-measure the food as misjinkzd suggested. Unless the fish are juvies or already thin and weak from disease, feeding them is not an issue if you won't be gone long-term.
Water quality is the greatest concern when you won't be there to monitor the tanks and perform your regular water changes. Overfeeding is far and away more dangerous than underfeeding, and those weekend and vacation feeders are horrible, messy pieces of junk.