This is part 3, of a 3 part tutorial for creating a custom module for drupal 7. If you haven't already done so, you may wish to look at part 1 and part 2 first. Anyway, here is the source code of this tutorial.
First of all, though, I have to apologize that I did not do a good job of keeping track of all of the changes made so far. I code everything before I start writing, so hopefully it is not too confusing.