I'm curious about other projects created in the same vein that are making money. I saw a typing tutor webpage posted here on HN, and a stock portfolio tracking service, but don't know if they ever became profitable.
My favorite two were
1. Software for people who sell and install granite countertops to help their customers preview what their counters are going to look like, doing millions of ARR.
2. Software to help high schools and colleges schedule umpires/referees for sports leagues.
There's so many 'niche' markets around that are worth millions if you can hit them (but they're not sexy like social networking or consumer mobile apps)