I think WoWWiki is a fantastic resource, and have found it to be very helpful so far. The instance guides and instance attunement information have been invaluable at times.
I have already made some minor contributions to try to enhance the information on leatherworking trainers and skinning trainers, notably adding coordinates to both the individual NPC pages and the lists of trainers, as well as providing some enhancements to the descriptions of the NPCs and their locations. I have verified every set of coordinates - none of them were lifted from other sources, as I wanted to avoid any inaccuracies. Hopefully this will save future generations of leatherworkers and skinners much frustration and time in locating the necessary NPCs, and I hope that someone will be able to add these for the Horde trainers and other professions.
As and when I have time, I'm trying to cleanup and enhance the leatherworking information and categories, and adding personally verified coordinates to NPC articles (for important NPCs, such as high level quest givers).
Doing exotic and unusual things with the MediaWiki parser to make things work a little better.