Action Bar Mods

BAB Bars Duugu

BAB Bars is a complete new action bar approach. It implements 'bendable' and 'flexible' action bars that are not limited to the standard 'rectangle' shape of action bars and action buttons. BAB Bars creates fully functional (additional) action bars in the form of curves, circles, waves, and any other shape.
WoWInterface

BarKeep Platykurtic

Features: All the main action buttons can be configured to have from 1-12 buttons. All the main action bars can be reconfigured to have up to 12 rows, so you can have 6 buttons x 2 rows, 3 buttons by 4 rows etc. This is done still using the Blizzard button code for compatibility. All the main bars can be scaled independently of one another. All bars can be hidden if you want, some using the Blizzard options from the interface menu, others using BarKeep. It uses an event / hook based structure for minimal CPU usage. It uses Blizzards buttons (and button code), so pretty much it's always compatible if Blizzard make any changes. Its really light in use - doesn't use a lot of memory and CPU cycles.
Config: /bk or /barkeep
WoWInterface

Bartender4 Nevcairiel

Bartender4 is a full ActionBar replacement mod. It provides you with all the features needed to fully customization most aspects of your action and related bars. Features: Support for all Action Bars and all related bars: 10 Action Bars, Stance Bar, Pet Bar, Bag Bar, Micro Menu, XP/Reputation Bar. All Bars are fully customizable (Scale, Alpha, Fade-Out settings). Very flexible and customizable Show/Hide driver based on Macro Conditions. Additional Layout and Paging settings for Action Bars: Page all bars based on Stance or Modifier, Possess Bar support, Custom State driver support with Macro Conditions. Options to hide specific elements of the buttons (Macro Text, HotKey, more could be added on demand). StickyFrames support, ButtonFacade support, Easy Hotkey Binding using KeyBound.
Config: /bt or /bar
WoWInterface, Curse

bBars Wildbreath

Lightweight complete replacement for default action bars with config mode (bindings, positions, scale and etc.)
WoWInterface

Button Forge Alternator

Button Forge is an Action Bar addon that allows you to create completely new Action Bars (as many as you want). Each bar can have up to 1500 buttons organised into rows and columns (up to 5000 buttons total). Your existing UI wont be changed by Button Forge, it will continue to function and look how it currently does. The bars you create are totally independent allowing you to simply and cleanly add additional action bars to your UI.
WoWInterface, Curse

Dominos Tuller

Dominos is an action bar addon which includes the following features: 10 action bars, pet, class, menu, and bag bars. Each one has customizable settings for padding, spacing, columns, scale, and opacity. A movable experience/reputation bar. Customizable paging. You can switch pages on: action bar pages, modifier keys, forms, and targeting. Customizable show states. You can tell your bar under which macro options to show. Fading bars. You can set your bars to fade out to a certain opacity when not moused over. The ability to customize showing empty buttons or not. Full button facade support, Keybound support, Sticky frames, The ability to move buttons in combat, Buff and debuff highlighting (optional), A movable casting bar (optional), A movable roll frame (optional), Configurable right click targeting, Configurable self cast key settings, Possess bar support.
Config: /dom
WoWInterface, Curse
Help: Wiki, Basic Instructions, Advanced Instructions
Review: WoW Insider

Geist Cidrei

Geist provides a twenty-five button action bar that displays under the mouse cursor at a keypress for quick and convenient access. How to use: Bind a key to Geist using the keybinding interface in the menu. Geist will display whenever that key is pressed with the mouse over the center button.
WoWInterface, Curse
Review: WoW Insider

Ion Maul

A macro-based action bar addon. It can stand on its own or supplement any other action bar addon or even the default Blizzard UI. This addon has replaced Macaroon.
Config: /ion
WoWInterface, Curse
Help: Ion Forum
Plugins:Ion Xtras

mActionBars Monolit

Flexible lightweight add-on that handles your action bars. Features: removes all the default action bars textures; supports vehicle, totem, pet and pitch bar; built in totem timers functionality for totem bar; custom exit vehicle button position; combat proof, no taint; styles action buttons' borders; out of range/mana coloring; supports stance and shapeshift bars; allows player to choose the orientation and amount of rows for each bar; grants the ability to set custom position size and spacing between the buttons; allows user to set number of visible buttons for each bar; the ButtonsStyler module allows to hide/show hotkeys, macro names, item count numbers, and also to set custom font for each of those text fields; key-bindings shortcuts; built in HoverBind functionality (/kb to enter bindings mode); supports MicroMenu bar; option to show bars only in combat; 2 special bars for raid marks and world marker flares.
Config: Lua
WoWInterface

nMainbar Neal, ballagarba

Smaller Mainbar (hide the menu and bagbuttons), Skin the actionbar, vehicle, pet, possess and stancebar buttons, out of range coloring, changeable fontsize of the macronames, hotkeys and counts ore hide them, hide the gryphons, .. and many more. This addon is part of the Neav UI package.
Config: Lua
WoWInterface, GitHub

OPie Foxlit

OPie is a radial action-binding addon, enabling you to bind groups of infrequently used actions to a ring that appears when you trigger it using a hot key / mouse binding.
Curse, OPie
Help: Warcraftic Movie
Review: WoW Insider

rActionBarStyler zork

Small mod to edit the position and scaling of the default ActionBars.
WoWInterface

Auras

AdiButtonAuras Adirelle

Displays aura information directly inside action buttons. AdiButtonAuras is a rewrite of Inline Auras.
Curse

Cooldowns

OmniCC Tuller

Addon that adds text to items/spells/abilities that are on cooldown to indicate when they'll be ready for use. OmniCC should be compatible with any addon that uses a cooldown model.
Config: /occ or /omnicc
WoWInterface, Curse
Review: WoW Insider

tullaCC Tuller

Minimal addon for displaying cooldown text on action buttons, inventory items, etc. A lite version of OmniCC.
WoWInterface, Curse

Food/Water/Potions

AutoBar ToadKiller, MuffinManKen

AutoBar is a Multi-bar mod that automatically adds potions, water, food, quest and other items you specify into buttons for easy use.
WoWInterface, Curse

Buffet Tekkub

Buffet is a simple water/food managing addon. It edits macros on the fly (out of combat) to provide you with the best food, water, potions, stones, and bandages.
GitHub, Curse

Skinning

Masque StormFX, jjsheets

Masque (Formerly ButtonFacade) is a dynamic button skinning add-on.
Curse
Skins/Plugins Masque: Curse, WoWInterface

rActionButtonStyler zork

Small mod that edits the textures of the default ActionButtonTemplate. Also adds range and mana coloring.
Config: Lua
WoWInterface
Styles: WoWInterface

Misc

FlyoutButton Custom another

Custom Flyout buttons similar to Blizzard buttons like traps and teleports. Now you can make your own buttons!
WoWInterface, Curse

tullaRange Tuller

tullaRange is an addon that's main purpose is to make standard action buttons appear red when out of range. Colors for both the out of range indicator, and the out of mana/energy/rage indicator are customizable via the in game GUI.
WoWInterface, Curse
Review: WoW Insider