Recommendation for software that creates synchronous movements

Hi everyone - I am after a program which would allow me to animate illustrations that I create in Photo shop.

What program do you recommend?

Ive been using An for quite sometime and love it but with this particular program everything is separated having its own movement points to each piece.

Id like to be able to create something like say a snake where its whole body moves around and twists and turns.

Like this clip at the 7 second mark..  Venomous snakes - Cartoons - Childhood fairy tales - YouTube

The animations from after this snake scene look like they've been done in An.

Cheers.