Cannondale still has their Scalpel MTB, which uses flattened carbon chainstays to flex as if the bike had a short-travel rear suspension. Same principle for their S.A.V.E. feature.

Look's 566 frame is designed similarly, too.

I'm seriously considering a bike like these for my next road bike. My CAAD8 is fun, and while it actually rides nicer than my Langster, I think I'd like something smoother.