My friends Gavin, Uri and I made a math website. It's a work in progress, but it's shaping up to be pretty cool!
A few years ago, I started asking my Facebook friends for suggestions for how I should spend Thursdays (my only day off). Every week, I devoted myself fully to whichever choice got the most likes, and write about the experience afterwards.
Saddened by the state of online dating, I made a Tinder profile offering to platonically accompany anyone on anything they'd always wanted to do (within a few ground rules regarding legality, cost, and maliciousness). I got hundreds of suggestions and went on 25 non-dates over the next two months.
The project was subsequently picked up by about a dozen media outlets, including The Daily Dot and News.com.au.