Equipment Managers

ItemRack Gello, Kharthus

This is a mod to make swapping equipment easier. You add equipment slots to a bar and mouseover on the bar will create a menu of all items in your bags that can go in that slot.
Config: /itemrack
WoWInterface

Outfitter Mundocani

Allows you to create multiple outfits and equip them with a click of your mouse. You can layer outfits, create outfits optimized for a particular attribute (ie, fire resist or maximum defense), and have outfits which automatically equip based on events like mounting up, stealthing or changing stances and forms.
WoWInterface, Curse
Review: WoW Insider

Gear Ratings

Gearing Guide crazysheep

This addon will show the priority of the item based on the stats that item has. The priority is built upon ElitestJerks stat priorities for each class. out of the classes that can wear the item, the addon automatically sorts the list to show at the top which class is best suited to the item.

This addon can in turn help people in dungeons as well as raids, as it will show how good the item is for the players class and spec, also useful when gearing their offspec, no need to research websites to find out what items are best.

With the tooltips showing class specific information, even questing now can be made easier, see the item has priority? Then your class can wear that item, check out the number, if its a low number its not perfect but wearable, if its near 14 or above, its really good for your spec!
Curse, WoWInterface

Pawn VgerAN

Pawn performs item value assessments to make it easy to decide which items are better than others. It's similar to mods such as Tank Points, but much more general, and applicable to any class and situation. You can use it to help create multiple gear sets, or decide whether to give up those ten points of stamina for two more points of fire resistance. Pawn is a mod for hardcore World of Warcraft players. You're probably not going to like it if you're not the sort of person who agonizes over stats and itemization. But, if you're the kind of person who goes through Thottbot looking for exactly the items you want for your gear sets, builds Excel spreadsheets, installs TheoryCraft... well, Pawn might just be right up your alley. If you can't bear the thought of hand-editing configuration files in Notepad, turn back now.
Curse, WoWInterface

RatingBuster Whitetooth

Unlike fixed percentages such as 2% critical strike chance, combat ratings diminish in potency as your character increases in level. 2% crit is the same at every level, while 28 critical strike rating grants 4% crit at level 34, 2% crit at level 60, and 1.27% crit at level 70. This mod converts combat ratings in your tooltips into percentages for your current level. It also gives a Stat Summary for comparing gear. You can choose what stats you want to see.
Config: /rb win
WoWAce
Review: WoW Insider

WeightsWatcher IQgryn, dpsthree

WeightsWatcher gives you an easy to use way to compare gear based on the actual stats, not just the item level. Currently, all base stats and gems in non-crafted sockets should be handled properly. Also, gems are suggested based on the weights you have enabled. Note that enchants are not currently included in the scoring (this includes crafted sockets), because they can be added to any new item as well. All weights can be changed as you see fit, and you can create and enable as many or as few as you would like. The current version includes the default weights from the fine folks at Wowhead.com, which are tuned for level 80 characters. Endgame players will probably want to create hit- and/or expertise- capped weights, which is easily done by copying an existing weight and setting the appropriate values to 0.
WoWInterface

Inspect

InspectEquip emelio

InspectEquip attaches a panel to the inspect window that shows a list of the character's equipment sorted by source (i.e. Raid: Ulduar, PvP, Crafted...). This gives you a quick overview of a character's equipment. InspectEquip also adds detailed item source information (including boss names, item prices for Emblem rewards etc) to all item tooltips.
Curse

InspectFix oscarucb

The Blizzard API for performing character inspection has fatal design flaws (namely, it's stateful yet client-oblivious). All UI elements that perform character inspection, from the Blizzard inspect frame to many addons that perform hidden inspects for various purposes, are forced to use this same API and frequently step all over each other while doing so. What this means for the end user is the more addons you install (especially raid/party/character related addons) the less stable the Blizzard inspect UI becomes. Common failures include the inspect window suddenly and inexplicably changing to show incorrect gear or talents, tooltips that suddenly stop working, or lua errors regarding the Blizzard_InspectUI.
Curse

Misc Gear Mods

Bimbo Tekkub

Bimbo is an equipment optimizer. Bimbo will scan your equipped items looking for missed enchants and gems. Unlike be.imba, Bimbo won't critique your choice of enchants, gems, stats or talents. It will not "grade" or "rate" your gear in any way, it simply looks for enchants you've overlooked.
WoWInterface, Curse, github

CloseUp totalpackage

Allows you to zoom, reposition, and rotate the UI's builtin models so that you may get a better view. Should support all models that you can interact: Dressing Room (including Auction House's), Character Info, Inspect, Pet Info/Stable, Tabard, Mount/Companion.
WoWInterface, Curse

ItemLevelDisplay alar

ItemLevelDisplay adds a tiny layer on each equipment slot in your paperdoll frame showing ItemLevel, Socket status & Enchant status.
Curse

MogIt Aelobin

MogIt is an addon that will help you find the perfect item for your Transmogrification set! Database shows how each item in the game looks. Includes 3d tooltip showing how items look when you mouse over them.
Curse
Review: WoW Insider

oGlow haste

oGlow will light up your items, by adding a quality border to them. It will only display this border for common quality items and above.
WoWInterface

ReforgeSaver Jordon

Save and restore reforging profiles for your equipped items. If you dual spec and require your items to be reforged each time you switch, you might find this mod useful. Equip the items you want and reforge them as desired. When you're done, type "/rfs save name" (replace name with whatever you want your profile named). Now, anytime you have the reforge window open and type "/rfs restore name" it will display the total price to reforge your equipped items and reforge them automatically after you confirm. You can type "/rfs list" to see all your saved profiles.
Curse