I won 4 Twitter contests a day (every day for 9 months straight) (2015)

I did something similar around 2009. You used to be able to sell RSS feeds on the Kindle, so I created a number of twitter bots that simply aggregated news from a variety of sources on a variety of topics and used Yahoo! Pipes to turn them into RSS feeds. Made about $10 - $12 a month for several years from that until they discontinued the service.

Previously:

https://news.ycombinator.com/item?id=20419756

https://news.ycombinator.com/item?id=13456638

https://news.ycombinator.com/item?id=10001364