WorldEdit

WorldEdit
WorldEdit is a SMP (And SSP) Bukkit Plugin/Mod that can remove or add blocks in a box, cylinder or sphere. Useful for terraforming and creating large structures.

Selecting Regions
To use WorldEdit, you have a Wooden Axe, (Wand), to edit blocks. Get the wand by saying //wand. A Wooden Axe will appear in your inventory. Left click a block to set the first position (While "Wand" is in hand), and right click another block to set the second position. You may also use //hpos1 and //hpos2. Those commands will select the block you're pointing at, this is useful if you don't want to fly around to select blocks. Another alternative is //pos1 and //pos2. This will set the position as your current coordinates when you say the command.