I do love to spend a good deal of time at Dan Brown's websites. And one of the most fun things to do is play the games/quizzes/treasure hunts he has posted there.
First up is "The Da Vinci Code Web Quest" which I've done a few times and had such fun in the process. The mysterious background music only adds to the, erm, tension?!
Check it out at this link: Da Vinci Code Web Quest
There is also a featured "Uncover The Code" challenge with similar eerie music aiding you on your way. It starts off pretty easily for the Dan Brown fan, but soon becomes very tricky. If you don't have the book handy you can select an image of the cover on the website to help you solve the clues.
So good luck with this one! Uncover The Code
The Lost Symbol is Dan Brown's most recent novel and is packed full of symbols, many of which are found on the base of the pyramid Robert Langdon finds. On this website, there is an unbelievably difficult game called "Symbol Quest". You just have to select the correct symbol from a cluster of symbols aided by a written clue. You are allowed just 3 wrong answers before the game is up!
Of course, you can always use Google to help you out, but see how many you can find based on your own knowledge!
Here's the link: Symbol Quest