NPC Catalog, a handy mod that lets you view all the items and their locations in your game.

Now you can search for any NPC and have it displayed right away, even without having to access the in-game menu. This is especially useful for those who are playing online with other players and don't want to wait for them to open their menu to see if their friend has the same item or location.

If you are playing offline, however, this can still come in handy. You can access your inventory and view all the items you own, their locations, and their prices.