A number of sites have been very useful to me in getting started with this game and figuring out some of the nuances that aren’t clear at first. Foremost is, of course, the Monkey House Games site (in particular, the forum there), home of MP‘s makers. Monkey House also maintains a YouTube channel where they post videos of full gaming sessions, which are a useful real-life look at the flow of the game and how many of the mechanics work.
Another frequent reference I use is the bk adams YouTube channel – a collection of video tutorials covering many aspects of game play ranging from configuring the flexible-but-complex “Arsenal” power to vehicular combat. Adams also maintains a blog where he posts some original characters, as well as conversions of other comic, TV, and game characters into the MP system. There are a wide variety of examples here of how to implement character abilities.
The V&V Emporium is another useful site; though much of the material there is focused on older versions of the game, new additions since late 2017 have been mostly specific to Mighty Protectors. Similarly, GiantGorilla’s Heroes and Villains also contains a variety of MP character examples.
2018-09-14 Update: In addition to his WordPress site, bk adams maintains a Blogspot address as well, which appears to have much the same content but in a better-organized fashion.