The list is simple. You have the name of the character, the writer who dibbed them and for what title. If you want to use a charcter listed here, contact the writer who dibbed them for permission.

Dib Levels:

Heavy	The character is unavailable outside said title. At most a small Guest shot might be negoiated under very special circumstances. A character that appears in a team book cannot be Heavy dibbed in his own unless the writer requests he be removed from the team book.
Major	The character is going to be a major player in this series. No appearances with out the permission of the writer. (or writers in the case of characters who have their own series, and are a major player in a team book as well, i.e. Superman in the JLA.)
Minor	The character is going to appear in one, maybe two arcs. Most of your recurring villains would fall into this category. The character is available, but check before using as you may need to know they're current status (injured, in jail, etc.)
Guest Shot	The character is appearing for maybe one whole issue, nothing earth shattering is going to be done with him so he is available for use. Check if you want to refer to the appearance