You cannot just setup everything, sit down and wait for users. You have to tell the public that the project exists and how they can use it. There are a couple of ways to do this:
Facebook, Twitter or Google+ are powerful tools to tell your friends and their friends about the project. You can share teasers for new content and do user education.
Every pingeb.org project should have a facebook page. To open a free Facebook page just go to the pages tool. The process is fairly staight forward and does not differ a lot from creating your own profile.
We found that the media loved our initial idea of a virtual library and even more loved the project as we started to promote local artists. We got lots of local press from all newspapers, major Austrian tech sites wrote about it as well as Germans.
We were totally shocked about the international response. One reader translated our short German press release and forwarded it to Engadget. And when Engadget or any other big blog writes about something, lots of other blogs will take the story too. See our press page for some (not all) clippings.
But as it is the case with the general public, you have to inform journalists too.
Ask your friends to tell their friends about the project or to post the site/Facebook page on their profile. Friends are the most credible source for their friends when it comes to tips.
Here again you see that a big team comes handy.