I just ran across this nice little program from company Realviz that, essentially, was made for storyboarding but really looks like what some of us would prefer to be THE machinima toolkit.
Even though the price tag is somewhat above the "Hey, let's start making machinima movies!" line, it might still be something to watch, as it supposedly is the first serious realtime 3D storyboarding software. Plus, it has non-linear editing capabilities...
A trial version can be found here.