I made dividend tracking website. I am a backend engineer, so the UI is simple bootstrap and I focus on having data I find valuable. I've been working on it since I finished University, so it's like 7 years, and current MRR at $740 isn't great, but at least I don't have to pay for hosting (and financial data sources are expensive). I believe that spare money should be invested in stocks, so I like that I work on something I use, and will be using in the following decades. The website is DIGRIN.com (DIvidend GRowth INvesting), good value for free users as well IMHO.