I just was looking for a web site that render 3D stuff for free. Do we have sth like this ?
+1 to what tildee said.
Note they work by a credit system, so priority goes to those with higher credits. You get credits by rendering.
Luckily, if you contribute your PC, it will render your animation first for you, and you still get 30% of the normal credits 
Finally, if you create an account with a non special password (or change it temporarily) I would be able to add some machines to render under your account, which would earn you a number of credits (and render for you) . Or I could render one animation for you under my account, since I have a fair number of credits