Colored Glow
To add item quality border coloring try oGlow.
Destroy Items
To automatically destroy items to make room in your bags try ExcessBaggage.
Sell Grey or Un-usable SoulBound Items
To automatically sell grey items (trash) when visiting a vendor try tekJunkSeller.
To automatically sell Grey or UnUsable SoulBound items try BagSaver.
Sort and Stack
To sort and stack inventory try BankStack, kRestack, JPack or NeatFreak.
AdiBags
AdiBags display the content bag in one view, gather into several sections using smart filters. It is heavily inspired by Nargiddley’s Baggins. Configuration is available through Blizzard addon panel, /adibags chat command or right-clicking on the LDB plugin.
Curse
ArkInventory
Inventory mod that displays all of your items in one bag. Features: unlimited number of bars, assign items to a category of your choice, assign categories to the bar of your choice, configurable bars per row, configurable width, display bank, bag, keyrings for current and alts across all realms, separate keybindings for bag, keyring and bank viewing.
Config: /arkinv
WoWInterface, Curse, Google Code, User Guide
Baggins
Baggins is a fully customizable set of virtual bags. Each bag can have many sections with different categories of items contained in them. There is an interface for defining your own categories based on rules.
Curse
Plugins - Curse
Bagnon
A group of addons that improve the way the player manages his or her inventory. A single, customizable display for your inventory and one for your bank, Color coded item slots and borders, View bank from anywhere.
Config: /bgn
WoWInterface, Curse
Bagnon2
BaudBag
Allows you to combine your bags into a single, larger one, yet gives you the power to choose which bags to combine. Great if you like to combine your bags, but don't want to always see the contents of your soul shard bag or ammo bag. Complete with a user-friendly graphical menu for changing how your bags will display. Use /baudbag, or the menu button on any of BaudBag's containers, to change the settings for this addon.
Curse
cargBags
cargBags is a lightweight and modular bag framework. It is designed that you can completely focus on how your items are displayed and sorted rather than caring about getting item info, updating your bags or handle interaction with items. You can define how many virtual bags you'd like to have and what items should go into it.
Config: Lua
WoWInterface, Layouts/Plugins
Combuctor
Combuctor is a bag replacement addon designed to help the player find things in his or her's inventory as quickly and as easily as possible.
Config: /cbt
WoWInterface, Curse
Combuctor: Custom Sets
Combuctor: Equipment Sets
EngBags Continued
EngBags is an AIOI with autosorting fully configurable. It separate your items as you wish between 9 dynamic bars of items. The sorting is made using categories, which you can edit. These categories can do full text search on item tooltips, which mean you can make a category that will include all items wich tooltip contain "Increases damage and healing". With this you can assing that category into bar 3 and you will have all dps equip items in that bar. That's an example, but you can do what you want with this in means of sorting. EngBags come with predefined categories that will bring you sorting out of the box. It also sorts the empty bag slots for diferent bag types.
Curse
ExtendedBags
Items in bags get an item quality colored border, Grey items sold automatically, items are repaired automatically, the bag buttons are replaced with item buttons (drag your four favorite items in the button slot), item buttons show item count, toggle bag-buttons and item-buttons with chat commands or [ctrl] + bagpack-button), open bags automatically in bank/guildbank.
Curse
gBags
Bagmod based on the beta version of the new cargBags2 framework. It is dependant on gMedia v2.11 or newer which must be downloaded separately in order to work.
WoWInterface
Genie
Full bag, bank and guildbank sorting addon with the following features: Changable sorting order, Ignorable items, Automatic action (here's where the genie comes in), Item stacking, Item moving (move special items to their special bags).
Usage: /genie work
Curse
Intextory
Intextory provides a text-centric representation of the contents of your bags, both on your character and in your bank. It has advanced categorization capabilities based on entering pure LUA code for filtering and sorting, giving you maximum flexibility to organize your inventory. High performance.
Curse
OneBag3
A replacement for the default game bags that combines all the bags into one frame. OneBag doesn't entirely rewrite the bag-handling interface like others do. It simply rearranges the bags into one and allows the default UI to continue managing the bag slots. This means that addons such as KC_Items, ItemSync, LootLink, and SellValue should be inherently supported. As long as an addon is compatible with the default game bags, it should work with OneBag.
Curse, WoWInterface
Stuffing
Minimalistic bag addon. It puts all your bags in one and your bank in another frame. A search function is also built-in.
WoWInterface
TBag
Provides an alternative bag and bank interface. Features include searching for items (in mail, etc.) You can also see and use the original default UI bags, which have slots free overlaid on top of them. There are also many convenience features, like highlighting new items, colored spotlighting, and purchase bank bags without having to unload the addon. A visual edit mode allows you to rearrange categories to your taste, and an advanced customization window enables you to completely configure every aspect of TBag.
WoWInterface, Curse