Although it is the fact that running the original World of Warcraft game client and have the latest patch installed in order to participate in the servers. However World of Warcraft add-ons are available and provide a degree of customization to the player's frontend so they can play legally with their original characters along with some fine-tuning enhancements that are done by 3rd party add-on developers.

As long as you are familiar with the World of WarCraft API, you can develop your very own add-ons that you can benefit from or share with others. The API is very extensive and with some good creativity, you can improve the user interface in World of Warcraft to better suit your gaming style and deliver a better experience without any fear of cheating or hacking risks.

If you won't get into developing, you can always browse a good number of World of Warcraft add-ons readily made available in the various fan sites around. Generally, you will find these types of add-ons:

Map Addons: anyone having trouble finding their way through the different instances and large maps will find the map add-ons very useful. Quest helpers and basic guides also fall under this category since maps are usually used. These add-ons take away the frustration in printing out a strategy guide or minimizing your World of Warcraft game to read a walkthrough or look at a static file.

Combat Addons: you find anything that'll increase the damage you deal, but you can find a great number of statistics related add-ons that can help serious grinders level up faster and see more on what's going on in the battlefield with visual cues and UI enhancements to boss and PvP battles.

Economy Add-ons: many of these add-ons compose of calculators and other financial related tools to maximize your funds in World of Warcraft and get the profits that you need when selling. Any serious WoW merchants should find some aid with these World of Warcraft add-ons.

Miscellaneous Add-ons: there are plenty of other add-ons to choose from that visually enhance the user interface or provide additional buttons that lead to informative panels.

These add-ons are easy to install and easy to remove, you can have a try if you want.