There are the Prada fragrance giveaways at http://theluxebooks.com/contests.vm, the $1000 sweepstakes to Bloomingdale's (plus a copy of the book) at http://www.harperteen-theluxe.com/contest/rules.html, the author interview podcasts at http://www.harperteen.com/features/podcast/index.asp, and apparently, when they were still promoting the book from within the industry, they hired the cover model to wear that dress and pass out advance copies at a party.
Just for kicks, here's a tidbit from the official book website:
Hey! I just wanted to say, LOVED your book and I COULDN'T put it down! Can you give us a hint to what happens in Rumors?" -- posted by: Nikki
Nikki, it makes me so happy to hear that you liked The Luxe! I'm putting the final touches on Rumors, and getting really dorkily excited about it, so I'm glad to hear you're looking forward to it too! I can promise a ton more gowns, a few big parties, the spilling of some crazy secrets, a lot of extravagant backstabbing, one good, old-fashioned makeover, and a wedding or two. I really hope you enjoy the sequel as much as you did the first book! xx