For developers, code and API documentation is very important, just as important as regular documentation is to most users. We always place a high value on proper comments and documentation in all of our projects. For a while we've been using the Drupal API Module for a self-hosted documentation site for our own Drupal modules. Recently, though we've decided to move that to public for any public modules that we or any of our developers are involved with/have released.
A short while after that first went up, the great maintainers of the api module (Jennifer Hodgdon & Neil Drumm) announced that version 2.x was coming out soon. Although it still is in final testing/development, we are now using that - it is not a mission critical site, and if we run into bugs great, then they can get fixed. In switching over, we did run into some very interesting conflicts that were easy to fix although hard to debug. Thanks to Jennifer Hodgdon for the help with that!
Currently, we have 5 modules up on the API site with all active branches:
Adding those and improving them for public usage, was also an interesting learning experience and our knowledge of Doxygen style comments and the Drupal commenting standards has been vastly increased. In fact, most modules require some adjustments and improvements for optimal display. For most of the modules we are displaying in fact we've committed or contributed patches improving the api documentation. Still some to do but doing that as time allows. Actually I feel a tutorial will likely be coming out about making better api documentation in Drupal projects.
So take a look at our Drupal Contrib api/development documentation, feel free to comment on any pages there or use the issue queues for the specific modules depending on the comment.