Blender (It is free) is very good, complicated at first but after an hour or so on it, the interface becomes easy! Here is a beginer tutorial (one which I followed and thoroughly enjoyed.) Also, the same question has been asked before, here is the other topic, you should find loads of programs, help and info there.
Hope this helps.
Josh
(p.s. One thing to remember is that animation is not easy and at first you will get nowhere, however stick at it and you will start to have fun and see results, but don't expect it to be instant.)