Pose Maniacs uses hundreds of skinless models from Poser and cycles them at 15-90 second intervals for gesture and quick sketch. It's really great because it keeps you on your toes, beeping in warning every time it changes models. The above were done at 60 seconds each.
The only complaints I have are that 1) Poser isn't the best source for anatomically correct models and 2) the lines of the musculature get confusing when the model is in an odd pose or at an odd angle (or both). It's not great for actual anatomical reference, but great for understanding pose, form and shape at interesting (and fuckin' weird) angles, at least as best as Poser can provide.
My figure drawing is, in a word, terrible, so I'll be doing as many of these as I can at some point each day to train my eye.