CrowBar is an addon that pops up a button when you have a container in your inventory that can be opened.
Click the button to open the container. Once all containers are opened the button will go away.
Hold down the alt-key to drag the button around.
Rogues might want to check out my LockSmith addon to unlock boxes in a similar fashion.
local ITEM_OPEN_CLAM = 'Benutzen: \195\150ffnet die Muschel!'
local ITEM_OPEN_CLAM = 'Use: Open the clam!'