Quentin one of my BIM students just shared a very nice screencast on the Drupal for the course programming. Now I have my students content private, but I do want to share you this YouTube by Michael Wesch of Kansas State University, its simply great.
For one of our modules called "node_access.module" (yes, the function and table exist, this is an expansion of it) we wanted an advanced multi-select. My college Wouter has created a pragmatic implementation 1/2 year ago. In the last weeks I finally got the time to refractor it.