If you are "into" wildlife then I can recommend "Planet Earth"..some truly wonderful footage on there.
As mentioned, Casino Royale is a good one.
I have just purchased Close Encounters of the 3rd kind on Blu-ray and can immediately see an improvement over the standard DVD.
Batman Begins is also a very good transfer.
I find the biggest difference in quality comes with scenes with any water in them...instead of seeing a vast expanse of blue (as you see on most DVD's) in Blu-ray you can make out ever ripple and water droplet.
So Blue Planet will be superb when it comes out.
I have The Last Samurai on BD and whilst not being Tom Cruise's finest hour, the detail in the mountain scenes is breathtaking in it's clarity.
I have just pre-ordered Zulu as well. I have high hopes that this will be superb bearing in mind the location in which it was shot.
If you have a decent surround sound system as well, DTS soundtracks give older films a new lease of life.
HTH
Rob