I would definitely add the Information Finding Championship hosted by @apolymask in this list. This is one of the most interesting and ambitious contests that brings together people of all different skills and knowledge, and is a contest that continually evolves based on the people participating in it (very much like Steemit).

Plus there is a great community of people who are all very supportive and encouraging, so it provides a great environment for newbies and minnows.
https://steemit.com/contest/@apolymask/updated-rules-and-information-about-the-information-finding-championship