WoW Mods are modifications and extensions to World of Warcraft’s user interface (UI). WoW Mods (also referred to as add-ons) provide interface enhancements as well as additional options not conceived by the developers at Blizzard. Some UI Mods simply change or improve the aesthetic appeal of World of Warcraft’s interface, but many actually provide improved information for your questing and raiding, helping you keep your bearings in the world and assisting you to coordinate larger groups in more ambitious adventures. They may also assist by automating some mundane tasks or providing macros to complex sequences of actions.
(I’d like to reiterate my impatient attitude towards cheats and hacks: They will not be supported in any way on this site. If a mod in any way attempts to exploit the game to give the player an unfair advantage, you should stay clear of it. Any tool that functions independent of the game should strictly be avoided.)
Most World of Warcraft Mods are free WoW mods. Blizzard Entertainment, the developer of World of Warcraft, does not develop or formally provide end-user support to these free WoW mods as they can’t possibly assure the quality and compatibility of the huge number of modifications made by the gaming community. However, Blizzard does support the mod development community with tools and support to third party developers.
You may find some paid mods out there as part of third party packages. An example of this is the waypoint add-on Brian Kopp includes with his excellent Brian Kopp’s Alliance Leveling Guide.
As you consider different existing mods, be aware that many mods created before the 2.0 release of World of Warcraft will no longer function properly with 2.0 and beyond. Blizzard radically changed the way add-ons interact with the game with 2.0. So before you download and install an appealing mod, make sure it clearly states that it has been updated and tested to work with the latest World of Warcraft patch.
Most WoW Mods are standalone mods that can be individually and independently installed. They need to be installed manually (they’re not like an official patch), so you should make sure you do so offline. Some mods are mods to existing mod systems, like the popular Titan Panel.
Please note that many mods really do enhance your enjoyment for the game, so if you’ve never experimented with them, I recommend giving them a try. However, I do suggest taking some time to evaluate and consider different mods before running amok and installing dozens of them. Installing too many mods can decrease your performance and increase the possibility of different WoW add-ons conflicting.
For the time being, I will provide resources to assist you in finding good sites to explore for mods as well as a page dedicated to the most critically-acclaimed UI WoW Mods.