I like the nuke waste plan proposed by an Omni magazine writer back in the 80s:
We build a huge expanse of concrete in a dry climate or use one that already exists, say, a Texas Tech commuter parking lot. We put some little channels around it to catch run-off. We pile the waste on the slab, hottest stuff toward the center. We build a fence at some safe distance and put signs on it: DANGER! CROSS THIS FENCE AND YOU WILL DIE! There will admittedly be people willing to cross the fence. Just think of it as evolution in action.