People who, ah, want to have more control over their lives like to believe that Quantum Mechanics says that by thinking positive thoughts you can live a better life.
Personally, I believe that by thinking positive thoughts you can live a better life. However, making the connection to Quantum Mechanics has been a stretch. One of the more famous books on this matter, The Dancing Wu Li Masters interleaves modern scientific thought with mumbo-jumbo resulting in an entertaining but totally bogus argument as to how one's thinking affects one's place in the Universe.
Now, this Wired article at least raised the issue in a way that got me thinking about it again. Interestingly, the author doesn't say that he has the answer - just that certain holes in the way our theories are described, especially as relates to the notion of an "observer", leaves open the possibility that a connection could be made in the future between biology and awareness and how the world works.
More: Wikipedia article on Wheeler's Choice Experiment.
Wikipedia Article on the amazing Double Slit experiment (with pictures!).