20 years ago, I was a college kid who built a running log website as an alternative to keeping paper records. My college cross-country team lived all over the country, so this let us keep each other accountable during summer training. It was fairly early in the Internet, before GPS watches and not many runners had heart rate straps. It got featured in Women's Health and Runners' World (UK edition) magazines.
When I interviewed at Microsoft my senior year, this gave me a ton to talk about. It was real experience building a product and having customers. I could answer questions with something real and different than the other candidates. I know I bombed two of my interviews, but I ended up doing 7 interviews on the day and getting an offer.
The website is still around, but I haven't done anything to it other than delete the production log that fills up the server disk occasionally in the last 15 years. I don't know why anyone uses it, there are much better options. I still run and I certainly don't use it. But the server bills are cheap, so it lives on.