Since we've just launched our open source project, we are currently looking forward to promoting it. The difficulty is that there is relatively little written on how to promote a project.
A good search on "how to promote an open source project" turns up only a handful of resources, most of which are more distribution specific than web-app specific.
The best resources I could find were:
http://lextm.blogspot.com/2008/08/promoting-open-source-projects.html
http://stackoverflow.com/questions/95710/how-do-you-promote-advertise-evangelize-your-open-source-project
Any further ideas?