Stonehearth and Radiant Entertainment team
Well, without their work, we would have nothing to share here :)
http://fontawesome.io/icons/ for having incredible good, useful and easy to use icons.
https://api.imgur.com have a good and easy to use API to upload and host images, so every image here is actually hosted there (not in public galleries).
Excellent solution to avoid bots without all the problems from those terrible captcha services.
Tech forums and communities
Multiple sites ranging from the simple w3schools.com to the powerfull stackoverflow.com and any other in between that you go cry for help whenever something fails and you are too stupid to realize why. :(