Simple Backpack "Pick up and drop"

Hey... I need to find a tutorial or a basic project that includes some sort of backpack like world of warcraft.

What i want is a Simple yet effective Backpack... "Press B" Gui opens shows a bag with slots and if i press "t" it will store that item into the backpack so i can then drag the item into the scene and will be in game. I'm creating a FPS and i want to be able to store say a health pack and then drop it whenever i need it.. Does anyone know of a pack/tutorial that covers this?