Anim8or can be downloaded free from www.anim8or.com and the same site provides a number of tutorials to get you started. One of the tutorials is included here with additional animations to help you - follow the links at the top or bottom of this page. Note that my Anim8or tutorial begins with the making of a static 'eggplant' (the process is rather different to Google Sketchup) and then gives an animation exercise called 'Simple Walk' (a robot bird).