I just discovered that there is an iPhone application for Harry Potter style moving portraits. On their web site they have an example how to embed it into any web page. I was surprised how simple it is.
A comedic blogger on buzznet is lire the whole series for the first time and reviewing it chapter par chapter. A good way to vicariously relive the joy of discovery, just don't post any spoilers :P
The balloons are designed to promote the Half-Blood Prince DVD and are part of a competition to win a Deathly Hallows set visit and cameo role in the final films.