Fast Building Mod 1.8, 1.7.10, 1.7.2 is a mod used to lay down multiple blocks quickly. Originally designed for building bridges, it has many other uses. Hold control and place a block, it will place as many as possible in that direction till it hits something or you run out of blocks to place. Very useful for bridge building. Even in creative, it will only place as many block as as you have in the stack!

It can do both vertical and horizontal placement. It modifies only the ItemBlock class only. Not many mods do this (that I know of), so should be fairly compatible.