There’s a site called Fictish for communal storytelling–you write the first part (called a chapter, but they’re usually far shorter than the average novel’s chapter), then someone else writes the next chapter, and so on. It can be fun.
Every so often (I think monthly?), they have a competition (which isn’t much of a competition). If you’re one of the first x-number of people (25 maybe) to satisfy the competition rules, you win a $10 Amazon gift card.
The conditions are trivial–create an avatar (only need to do it once), write a short bio (again, only once), start a new story by writing a short first chapter, continue someone else’s story by writing chapter 2 or 3 or whatever, and provide a like and a comment on a story.
There’s no voting or anything like that. It’s in beta, though, so that might change. I’m also under the impression that it’s only for US, Canada, Australia, and the UK residents. Others can participate, but they can’t win a prize.
Last I checked, they still had 10 gift certificates to award.
So if you enjoy communal storytelling (and maybe want to grab a quick ten bucks), check it out.
Main site: https://www.fictish.com/
Current competition: https://www.fictish.com/write/competitions.html
FAQ: https://www.fictish.com/write/info/help.html