Meet the Sweight Weight Plates: plates that sway in a pendulum style to give you a more intense workout with lower weights. When mounted to a bar, you will be required to use a slower, more controlled movement to perform exercises.
You can use these for squats, deadlifts, presses, curls, and lunges. You can get these from 10 to 45lbs. The complete set is available for under $200 at this time.