I have just purchased your screencasts from the site, and after watching them both fully, I started to follow the first step by step. At the point where you make it clear that the Post-Authorise Redirect URL (around the 18 minute mark) should not have a trailing slash is now causing some problems.
You see, however I edit this, Facebook seems to automatically add the trailing slash, which is then causing the double-slash effect when you first authorise the application.
Have you come across this ? Do you know if there is some way around it ?