You really have to look into the specific organization you're donating to, be it for human or animals causes. Some "charities" take ungodly percentages of the money to fill their paychecks and only give pennies to those who actually need it.
I tend to give to animal charities more like the ASPCA because things like animals mutilated by dog fighting, cat hoarding, neglect and general abuse INFURIATES me. Not because, ohhh look at cute widdle doggy woggy!, but because those animals are like children - they are DOMESTICATED animals that were bred to depend on humans for shelter and care. Now there is a staggering overpopulation of animals due to human carelessness of a situation we created. It's disgusting.
I also like donating to breast cancer research because I am *told* that I am paying however much of a percent towards a mammogram. Having a definitive answer like that helps.
As far as donating towards starving people goes, there has also been significant research into the idea that simply giving to poorer countries, like Africa, hurts more than helps. You can give and give and give, but all that does is foster dependence rather than independence. For instance, once a charity moves on after teaching a tribe how to use water wells or other equipment, the tribe more often than not only sells the equipment and falls back into old ways of starvation and poverty. The war lords are the real issues we need to face over there. It's a strange issue.