The big news going around scientific circles is the GFAJ-1 strain of bacteria discovered at Mono Lake in California. It was artificially manipulated into accepting arsenic as a substitute for phosphorus. A much more detailed write-up on the development can be found IN THIS DISCOVERY MAGAZINE BLOG.
While the discovery is not as world-shaking as some sources have hyped it, it is still huge. This strain of bacteria is doing something no other lifeform has ever been seen doing: using am element besides phosphorus for its driving energy. It hints at just how life can evolve and adapt to extreme conditions beyond anything we previously thought possible. As many others have pointed out, this indicates that extraterrestrial life, if ever found, could take radically different forms than we've previously assumed (outside of science fiction, of course.)
Anyway, I'll be following developments of this story with interest; its easily the biggest discovery at the frontiers of biology since the extremophiles found at volcanic vents at the ocean floor.