Is there any way to exploit a floating sand/gravel glitch in minecraft?
Solution 1:
Rather than trying to do it in-game, you can use MCEdit to achieve the same effect. In MCedit, select an area of air and use the Fill & Replace tool to select sand. Save your world, and voila: floating sand.
Apparently, sand doesn't start falling until it's interacted with.
There's also a weird interaction between sand and torches, in that sand will float above a torch:
Minecraft physics is the best kind of physics.