I got the Shrek Movie Collection (Shrek 1-3, all in 3D) last week; it was bundled with a Samsung 3D kit I purchased. While the 3D is actually well done I've never been a fan of the subject matter. The collection is in like-new condition (only watched once).
I also have Despicable Me in 3D. Again, while the 3D is good the story didn't do anything for me. The disk was only watched once and it and all the packaging are in perfect condition.
I'd be interested in trading either of the above for Avatar 3D or Megamind 3D in comparable condition. I did the online redemption voucher for Shrek 4 before watching the movies so I could add that in as well when it arrives (10-12 weeks according to the website, hopefully sooner according to other users who redeemed the voucher).
If anyone is interested, please feel free to drop me a PM. I can provide photos of the discs and I work in downtown Boston, MA so if anyone works in the area as well and is interested I can bring the discs in for an in-person swap.
EDIT April 28, 2011: My Shrek 4 Blu-ray arrived today as well (really fast processing on Samsung's part, less than a week since I did the online voucher) so I now have the complete Shrek collection. It has the best 3D of the 4 films though oddly, it has a 2.35:1 aspect ratio whereas the others were all full screen.