Hip trendy startup software folk hate "Marketing Guys". Usually for good reason, since they tend to swoop in and steal the best donuts at the conference breakfasts by distracting you with buzzwords like "SEO" or "global goal-oriented output funnels" or "Rebecca Black".
This mentality drifts over to open source software, too. We like to think that open source is pure, that it's unadulterated. That marketing an open source project is silly.
That's just silly.
Prior to GitHub, word about open source projects travelled primarily through word-of-mouth and messenger bicyclists. The largest open source project had three users and two developers. I think it involved a lot of twine and glitter.
Anyway, I digress. When GitHub launched, you could log into your dashboard and see the News Feed front and center, giving you a glimpse into what developers you're following are working on, what they're watching, and so on.
This was insidiously subtle, but ended up being one of the strongest advantages of moving your projects to GitHub. Your followers watch your projects, which in turn gives you more exposure to their followers and so on.
I think the problem is that a lot of developers stop there. They see a modicum of support from their GitHub followers and call it a day.
You should do more!
Marketing your projects is important. Open source is fantastic, and noble, and awesome, yes. But if you believe your project has value — which you probably do, since you spent time on it — you should try to get it in the hands of as many people as possible.
Get your project's name out there. I can't tell you the number of times I stumble on this tiny, underfollowed project and it completely blows me away. This isn't an ego thing; I want you to whore yourself out. Did you spend two days hacking out a way to convert my data between two services I use? I would absolutely love to discover that. If it's worthwhile to you, it's probably worthwhile to someone else. They won't use it unless they learn about it.
The easiest thing to do is to tweet about your project. Retweets can be extremely beneficial to a new project, and people honestly love to tweet 1) links, and 2) cool things. It makes them look hip. That's great; help them look hip by tweeting your new projects and code snippets.
My favorite marketing of all time is documentation. We all loathe sleazy marketing, and by definition I like to think documentation can't be sleazy because it solves a real purpose: teaching everyone about the project.
The best part, though, is that documentation is linkable. It's indexable. It's tweetable. Particularly if you have a nice, coherent one-page overview of your project that lets people jump in and immediately "get" it. Check out Bundler's docs. Or the Rails Guides. Or the interactive Try Redis app. They're very inviting, very welcoming glimpses into the project. As much as I absolutely adore a nice README on GitHub, they still can't be as impactful as a thoughtfully-designed page.
This matters to me because the more everyone markets their projects, the better off we all are. It's not a zero-sum game. Better documentation, better relevance in search engine results, more project activity, more contributions, happier users. I like it.