My Mac App Store only scanning app (https://www.pdfscannerapp.com/) still makes approximately this much a month after nearly 15 years on the store (I published it on day one when the store was realeased) - all updates since then have been free, so I'm just selling to new customers. It's a hobby project that keeps me into Apple platform development and allows me to work on it in bursts (like the last update for Liquid Glass) and then let it rest for a while (if Apple doesn't break any APIs).

My wife runs https://www.saviament.com/, an open-access educational website in Catalan. She also sells printable content following the same style as the website, which has exploded in popularity this year and has become a decent source of income.

I love fountain pens, and use handwriting as a kind of superpower to remember everything I need to at work.

So I started an online fountain pen shop: https://www.bottleandplume.com - it's focused entirely on all the stuff I love: fountain pens, fountain-pen friendly paper, bottled inks, and everything else you'd want or need if you were getting into the hobby, playing with .

I got lucky with timing a few marketing things and it's grown considerably, with lots of repeat customers (I'm really active in the community, not as a business strategy but as a result of my fountain pen addiction, so that helps).

I have a tech job that pays the bills so I'm more focused on having fun and building the fountain pen store I wish existed than on squeezing every last dollar out of my customers and business. It's a lot of work but I'm really enjoying it.

I made https://meetinghouse.cc as a way for twitter people to put themselves on a map and write a bio, and what they're looking for. It's a way to find and be found, if you want to see who's interesting nearby for friends, dating, new parents meeting new parents, etc.

Pins cost $12, there are 474 pins placed so far. This keeps the quality high (there are no spam pins, only real people) but will fundamentally limit the growth, I think.

Because I was frustrated of the pricing and feature list of TrainingPeaks, I've built my own training planning and analytics platform for endurance athletes (and coaches too!). It is called Tredict (https://www.tredict.com.) and it covers almost everything for runners, cyclists and swimmers over training effort forecasting and prediction, a comprehensive training log, training plans, workout planning, Vo2Max calculation, FTP assessments and collaboration with other athletes and coaches, equipment tracking and so on and so on. Quite a lot of things TrainingPeaks offers too. It has integrations for sending and execution of planned workouts to your watch with Garmin, Wahoo, Suunto, Coros, icTrainer and it receives executed trainings or health data from Polar, Dropbox, Oura, Withings and others! I think I did more then 15 oAuth integrations in total over Tredict's existens? And the platform offers an oAuth2 API for 3-party integrations on its own.

The payment model is a pre-paid model for 12 months of write access to your calendar. It brings ~500-600 Euros (before taxes) a month since 6 years.

https://www.tredict.com

I run a keywords research tool, it scans posts across social media sites like bluesky, mastodon, hackernews, etc.

KeywordsPal.com

It's actually super interesting the technical aspects to scan 50k posts a day for as cheap as possible. I write about it here: https://keywordspal.com/blog/building-multi-platform-content...

I also built it as a result of being unsatisfied with f5bot

I run SideProjectors - https://www.sideprojectors.com - a marketplace where people can buy/sell their side projects and businesses. I've been running it for over 14 years now.

I run Brick Ranker a website that tracks the value of LEGO sets and minifigures. You can also signup and catalogue your own collection so that you can track it's value or just see what you own.

It makes around $500 a month from a mixture of adsense and affiliate schemes. Would be good if I was making more but I've automated most it so I spend maybe 1 hour on it a month.

https://brickranker.com

https://www.youhere.org: "Want to know who showed up?" is the tag line. It's an app-based attendance service for teachers/coaches/band directors/conference organizers, etc. I'm a teacher and it scratches an itch I had (students not showing up to class). Been hitting the $500/month more and more often now (even after server fees).

Not sure if blogging, collecting blogs, and interviewing people about blogging is considered a side project but ever now and again, depending on how generous the people on the other side are, I hit 500/month in donations.

Everything I do is free for everyone but for the past few years I’ve been running an entirely optional membership program that starts at $1/month.

I’m (probably naively) a big believer in kindness and I keep refusing to monetize what I do in any other way.