You are probably thinking about the Talgo trains currently in service on Amtrak's Cascades line in the Pacific Northwest. These are European desiged railcars (from Spain, I think) with tilt technology. I have never ridden them myself, but I hear they give a very smooth ride.Trainweb has all the information and photos you could ask for at http://www.trainweb.com/accommod/talgo.html
That page also has a link to Amtrak's Cascades website. And be sure to check out the 360x360 photos. They're very cool.
I'm sure someone can provide more information than I can, but this should get yuou started.
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Trust God, love your neighbor, and never mistake opinion for truth.
-Mr. Toy