The more easy program for make animation and free ;)
and directly format saved from Moi (SKP) is Sketchup!
http://www.sketchup.com/
see my little video ;) http://moiscript.weebly.com/video05-plug-su.html

of 2 sorts :
1- animation of camera so automatic transition between scene





2- or more elaborate any animation (physic, or moving objects) but depending of what you need! ;)



In any case you must have a renderer inside like this funny one light-up http://www.light-up.co.uk/ but it's not free 149$
or twillight 99$ http://twilightrender.com/


There is only one free without limitation for sketchup : Kerkythea but not for beginner!
http://www.kerkythea.net/cms/