LibItemCache-2.0

Still works in every version of the game, but has since been deprecated in favor of BagBrother.

LibItemCache is a library that allows you to query for inventory information of players and guilds, while keeping you abstracted from the source of the information. Internally, it checks whether the information should be queried from the server and, if not, it will search for compatible caches and request them the information.

More information on GitHub.