Warner Brothers has commenced a new sweepstakes on the official Harry Potter website, with the grand prize being a trip for four to the set of Half-Blood Prince!
The contest runs now through January 5th, and there are two ways to enter. First, you can simply visit this page and fill out your information. You can also add their Facebook application to your profile, and “for each of the first twenty (20) of the Actions you perform during each Entry Period, you will receive one (1) entry into the drawing for the applicable Entry Period and one (1) entry into the drawing for the Grand Prize Entry Period, up to twenty (20) entries into each drawing, per day.”
Full details can be found here. Good luck to everyone who enters! Thanks to HeartlessBlueAngel for the tip.