For my own sake, and of course anyone else who will find these useful, below are a list of resources that I use for WoW Classic. They are in alphabetical order.
CurseForge Addons – Find any addon you need for WoW.
Wowhead – A great resource for all things WoW Classic: items, questing, news, etc.
Wowhead Talent Calculator – Help you figure out your talents before you commit to it in game.