Try Blender. It's free. Its animation tools are on par with Maya, Max and friends. There are awesome rigs for it. It has a steep learning curve, but there are probably more tutorials (including video) for it then for any other tool out there...

Another option is to use learning editions of industry standard packages (for example, Maya PLE).

If you're interested in animation, Blender is too complicated, learning editions are too crippled and you're ready to spend some cash (roughly the same as ordinary edition of Poser), I recommend Hash Animation Master. I haven't used it for about 5 years now, but it has a well-deserved reputation of being both capable and user-friendly.