I've seen several people asking if there is some kind of "list of addon programming tips" site recently. There isn't, but I know there are a lot of great forum posts floating around, so I thought it might be a good idea to start a centralized list. I'm starting out with some of mine, but feel free to post links to your own posts, or to other posts you found helpful. WowAce posts are also fine, and I'll be updating the list based on suggestions posted in this thread.
Getting started
Common questions and misconceptions
General tips and tricks
Specific tutorials
See also:
Useful Information / Tools / Links for Developers