Pixar motion blur
Historically there are only two types of motion blur, 2d and 3d. The 2d one is post processed and the 3d one is done at rendertime. 3d motion blur is much more accurate but takes a lot of time to render.
Two years ago, Doug Sweetland gave a talk at 
Annecy where he explained how much effort it took to achieve a good looking motion blur and I would like to share with you some screenshots I took a while ago.
Very interesting, I found the new looney tunes short very inspiring regarding that aspect. Look at the quicktime version of the clip ( http://castfire.cdn.fm/video/121/816/2508/378252/coyote-mov_2010-07-22-035307-2917-1-2-0.2917.mp4 ) to scroll throught the frames. The bit where Coyote draws the forks is just mind blowing for 3D, same as the part when the roadrunner right after this shot steps back on the side of the road. This example goes back to the good old “smears”. Cheers mate.