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. Its unique style allows for desert-themed architecture.

Sandstone is one of two blocks that are unable to be climbed by spiders, the other being the far less explosion resistant sand.

History
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

Sandstone was added in the Beta 1.2 update on January 13th, 2011.