When I was an isolated kid in the English countryside my only connections to the computing world were "Public Domain" floppy disks. Mail-order libraries would send me one of the disks in their catalog if I posted them a pound coin taped to a piece of card. I've never forgotten how important those glimpses into a wider world were, and I'll always be grateful to the people who made their demos, games, and utilities freely available. They were a lifeline to me, and I always wanted to give something back in return. My first contribution was a 'desktop palette' of 16 colors I'd selected for an especially pleasing RISC OS background, which didn't exactly set the world on fire.
That set the tone for most of my open source career – when I release a new project, I expect a deafening silence. There are occasional exceptions, but most of them don't make sense to anyone else, at least at first. The majority get quietly ignored by me and everyone else, but a few I keep working on, and they occasionally get picked up by other people too.
The Data Science Toolkit has turned into one of those sleeper projects. Over the last few months I've had a lot of bug reports, which is the best measure of how many people are actually using the code! There have been some nice companion projects too, like this wrapper for Excel or the new API library for Node. It also powers OpenHeatMap.com, which also keeps growing like a weed entirely through word of mouth. Hearing about the uses has been fascinating; academics of 19th century American literature mapping the spread of place mentions, reporters analyzing documents to track corruption in developing countries, mobile real estate app startups, university alumni associations.
The common thread for everyone using it is that they're marginal, just like I was growing up. There aren't enough of them and they don't have enough money to tempt commercial developers. Young open source software grows in the cracks between profitable problems, and survives on a starvation diet of spare-time coding. This gives it the time to find its niche, its audience, in a way that a more conventional development approach never could. Slow-growing software has the chance to reach people who'd never be found any other way, so if you're working on an unpopular project that you love, don't give up!