A couple of possibilities, from my experience.
Trackbar noise will be transmitted through the floor and felt at your feet, as you describe. Check everything with your trackbar. I've installed one while the front suspension was drooped, and got this noise because the bar wasn't properly centered on installation. Re-installation with the vehicle on the ground and no more noise. A worn or loose bar (experience with both) will also cause this.
Sway bar bushings will also cause unibody noise.
Good luck.
Geoff