A YouTube channel with arrangements of popular songs, all by ear. All the sheet music is available for free.
I started arranging music so that I could play songs that I wanted to with a group of friends. I put also put them online because I thought some other people might want to play them too. Much to my surprise, the answer was a resounding yes and now the channel has over a million views in total.
I no longer arrange as frequently as I used to, because my attention is now more focused on programming in my free time. However, it was a whole lot of fun to make something that so many people enjoyed.