Cobblestone can be crafted and used in new ways in the crack pack.
Besides vanilla methods, cobblestone can be made in other ways:
Biomes O' Plenty:
Ars Magica 2:
It can be macerated and pulverized into Sand.
Turned into lava in a Magma Crucible.
Squeezed into a container to hold lava with the Squeezer.