Gany's Surface by ganymedes01
This is one of the three mods in the Gany's Mods collection. Gany's Surface adds blocks and functionalities related to the over world (duh). Poop everywhere! Detect when is raining, make armour out of wood, and have a nice cup of tea in the morning before going mining, just don't put the milk in first!
GasCraft by Emasher
GasCraft is an official addon for Engineer's Toolbox. GasCraft adds several gases to the game which while all functioning like normal Forge fluids, behave like gases when in block form. Different gases have different uses.