The Da Vinci Code's publisher bills it as "the most fun you've ever had on the web." For readers of Da Vinci Code Decoded the game should be a cinch.
The online version of Tracy Twyman's invaluable Dagobert's Revenge magazine.
The official website of Opus Dei.
Dianne DiNicola's Opus Dei Awareness Network.
The online version of Stephen Dafoe's Templar History magazine.
Among other resources available on his website, Dan Brown supplies a partial bibliography for The Da Vinci Code.