Any Joe Blow can write a handy application and release it as open source but what's the point unless other users (to make the project worth while) and programmers (to improve the project) can find it.
Uploading an application's source to Source Forge might be a start but as of now there are 171,886 projects listed... who on earth is going to find it amongst that lot?!
Making source code freely downloadable from ones own website is another alternative but you need to have a popular website to make that alternative viable.
Have any Stack Overflow users released an open source application and ended up with a reasonable user base and development support?
If so, how did you do it? What marketing techniques have worked well?