Sandstone

Sandstone is a solid block, crafted by placing four blocks of sand in a crafting square, in a square shape. This means sandstone can be created without the use of a workbench. Placed sandstone can be harvested with a pickaxe. Sandstone was added in the Beta 1.2 update on January 13th, 2011.

Uses

 * Sandstone can be used to make sandcastles, as the sandstone blocks are not affected by gravity.

Origin
Sandstone is a player made mod that Notch made official, albeit with a different texture. http://www.minecraftforum.net/viewtopic.php?f=25&t=120307

Example
http://www.youtube.com/watch?v=Abm7YdsjSck