Leigh Walton of Top Shelf fame has produced a massive Tintin sketchbook, accumulating sketches from the likes of Bryan Lee O'Malley and Kate Beaton. I drew the pic above during MoCCA this past spring.
Laura Hudson has a write-up of the sketchbook on Comics Alliance, and you can see the entire book's Flickr Set!
Some of my favorites:
... and something like 500+ more HERE.