Backpacks can be acquired with /backpack give. This will put an empty backpack (chest) in your inventory.
Backpacks are accessed by holding them in your hand & right clicking.
Since backpacks are physical items, you can store items in one, then throw it to another player.
Warning: Backpacks should not be renamed with an anvil (this will delete the backpack). Instead, use /backpack name
/backpack: Base backpack command, shows help dialogue
/backpack give [name]: Gives the player a backpack (if no name is specified, the name will just be "Backpack")
/backpack name <name>: Name the backpack in your hand
backpack.use: Gives access to /backpack (and all sub commands)
No permission is required to open a backpack.
http://dev.bukkit.org/bukkit-plugins/physical-backpacks/pages/config-yml/
This plugin checks for updates on startup. You can disable update checking by setting checkupdate: false in the plugin's config file.
This plugin utilises Hidendra's plugin metrics system, which means that the following information is collected and sent to mcstats.org:
Opting out of this service can be done by editing plugins/Plugin Metrics/config.yml and changing opt-out to true.
http://dev.bukkit.org/bukkit-plugins/physical-backpacks/pages/videos