I wasted hours on these types of games back in the flash era, people were constantly releasing new ones with more types of sand and various effects and combinations, its a shame that whole segment of internet history was deprecated along with flash, good times.
It's not gone yet. One of my favorite places of this sort, andkon is still going strong after all these years. The toy category still has some of the sandbox stuff: http://andkon.com/arcade/other/toy.list
