Existing Communities and the Stealth Geek
We've all seen the stereotype of the open source contributor. He's unkempt, has a straggly beard, and lives in his parents' basement or under a desk at MIT. In a few cases that I could mention, this stereotype isn't too far from the truth, but it's certainly not universal. A lot of us, when away from our keyboards, can pass for normal humans.
Many open source developers (and potential developers) have other interests. If any of these interests overlap with the code that you're releasing, you might find an existing community. Joining an existing community is a lot easier than trying to create a new one.
If the community has even a few hundred members, you may find that one or two of these people have the skills required to make a positive contribution to your code. Even if they don't, they may know other people who do, or be willing to pay people who do.
This last point is quite important. I'm using the term community quite broadly here. A community in this context might be a group of companies that have the same need. A good example of this kind of involvement is CinePaint, formerly known as Film GIMP. This project was sponsored by a group of companies involved in movie production, as a fork of the GNU Image Manipulation Program (GIMP), to add support for things like 32 bits-per-channel color and HDR images that were needed by this group. These people were spending a lot of money each year on licenses for proprietary software. By sponsoring an open source project, they gained the use of an application that had exactly the features that they needed, the ability to add new features as required, and freedom from per-seat licensing.