How and When Will the Code Be Made Available to the Public?
The code needs to be placed in a publicly accessible repository from which it may downloaded. You may do this as a tarball in a directory available from your web site, especially for small programs. For more involved projects, there are many version control systems available that are commonly used and which allow users to view trees and modules and interact with them.
After you get the code posted and available, all that remains is to announce that the code has been released. You can do this on a small scale from your project web site, or you can post an announcement on a site like freshmeat.net.
Choosing to release program code that has been developed in a closed environment does not need to be difficult, but to be successful, some thought and planning are required. To give your project the greatest opportunity to be noticed and considered, you want to do more than post the code on a random web page and hope for the best. Take some time to think through the issues described here, and your release is likely to be a success.