Once you have an account on the Developer's Forge, you can share your module with the world. You don't need to have already written your module before adding it to the Forge. In fact, there are good reasons for adding it to the Forge before you begin writing it (so that you can have a source control repository, for example).
This recipe walks you through the process of adding your module to the Forge.
All you need at this point is a web browser, and an account on the CMS Made Simple Developer's Forge. This recipe assumes that the project you're publishing on the Forge is a module, but the basic steps are the same for all kinds of projects.