Mod Spotlight: TooManyItems
With the TooManyItems mod, you can become the master of your own world! (at least in single player, that is.) Whether you want to put yourself into creative mode, give yourself a 64 stack of stone, or get rid of that creeper that’s about to blow you to smithereens, all of these options plus many more can be available right from your inventory screen and just one click away! You can even save custom inventories and load them up without having to find all of those items again!
TooManyItems for 1.2.5 (Minecraft Forums)