I have a module that i have developed, and I want to post it on drupal.org to be available for other developers to download. How do I do that?
Essentially, you need to apply for a Git account in order to be able to commit the code in the Drupal.org repository, and create the project for your module. Before doing that, you need to approve the conditions for using Git repositories, and you need to set up your Drupal account to be able to commit code.
Alternatively, you can create a sandbox repository that, differently from the full projects, don't require you apply for a Git account, but don't allow you to create releases for your module.
If you don't want to maintain the module, the second option is maybe the preferable. If somebody is interested in the module, he would probably ask to become co-maintainer, and transform the sandox project in a full project.