For my project (https://www.robotshop.com/letsmakerobots/pet-work-progress) I need complex behavior and nice animation. My example is the NAO robot (http://www.aldebaran.com/en).
One of the things I am thinking of is mixing animation layers. Say you have one animation layer that does a basic biped walk. And another layer contains a balancing correction. And a third layer might contain head movement. Let's call them A, B and C.
Depending on the logic, I want to mix those layers. At a certain moment the mix could be 100% A + 10% B + 50% C. So all individual servos should be a mix of the values in each layer.
Some layers run in a loop, like the walking. Others run only once, like some gestures.
Now to program this all, I need logic on the board and on my computer. I have found the flowbotics studio software (http://www.flowbotics.com/learn-more.html). And atmel studio (http://www.atmel.com/microsite/atmel_studio6/).Also I have subscribed to aldebarans documentation (https://community.aldebaran.com) to get access to the NAO documentation. The last is actually the platform I would like, but of course it is dedicated to the NAO. Isn't there an open source platform that does this all?
I also need to figure out what hardware I need. It is clear that a microchip from the arduino is way to limited :).