I figured out how to get my figures to stay planted without resorting to python scripts and such. It's not perfect by any means since it requires the animation to be run with IK on, which imposes some limitations. But for an animation sequence where you want to keep the feet planted throughout, it works fine.

Imagine you want a figure to do a kind of shimmying dance (moving his/her torso, arms, head, etc around but keeping his/her feet planted in one place). Now, here are the steps I take:

1. Create the basic movements you want, using IK on for the legs or just brute-force posing the legs and feet to go close to where you want them to be during the animation.

2. Save your file so you can get back to this point if something goes wrong.

3. Go the frame 1 and hit ctrl-D to drop your character to the floor.

4. Turn on IK for the legs only.

5. Open the animation pallette (shft+ctrl+V)and scroll down until you get to buttock, thigh, shin, foot, and toe (both right and left) for your figure.

6. Use your cursor to select ALL keyframes for those figure elements (i.e., buttock, thigh, shin, foot, and toe -- both right and left) for frames 2 through the end of the animation. You should see a white box around the keyframes.

7. Press delete. (That's right, delete them! As long as IK for the legs is on, a new set will be generated which keep the feet planted on the floor, though you may not see the new frames in the animation pallette until you turn off IK.)

As long as IK for the legs is left on, the figure will now do his/her moves with the feet staying planted. If you turn IK off, the feet will stay CLOSE to planted --and may be better than the original animation esp. if brute-force posing is used to position the legs and feet-- but they will revert to moving slightly. But as long as IK is on, you should get the result you want.

Now, everyone do the shimmy!

Good luck...