Christianity Today asks "Should I Give a Cow or Cash for Christmas?" They look at giving to the poor in the world via animals, cash (whether as gifts or loans), and digging water wells. It's well worth reading.
If you want to give an animal, cash, or water, I'd like to commend World Vision to you out of the many good options. That's where our family gives.
For your convenience, Heifer International is another popular place to give.