Intel(alt): Track the status of world PvP objectives (towers, Wintergrasp, Halaa, Bone Wastes, etc.) using icons and countdown timers on the world map.
ZoneDefense(alt): WorldDefense and LocalDefense message handler. Add zone to alarms, ping the world map at alarm locations, handle "under attack" spam, customize message display (colors, format, etc.), and more.
AFK Fix(alt): Prevent clearing your AFK flag when addons send messages over hidden channels.
I have created several libraries for my addons which can make life easier for myself and other authors who wish to use them. Generally, if a library file says it was created by Tuhljin, you are free to use it so long as you don't claim undue credit. I like to hear from those that use my libraries since I like to know what is being used where and want to know how it works out for you so I can keep these things in mind should I update the library in the future. Some library files include detailed instructions on their use. In any case, you can always check out how my addons utilize them.
A list of libraries authors may be interested in is (allegedly) forthcoming. For now, if you see one of my addons doing something you'd like yours to do, from world map icon placement to interface options panel management, look at the included files and see if there's a suitable library facilitating it.