An old Russian satellite, Kosmos-2251 , and the Iridium 33 communications satellite collided over Siberia late yesterday. A very large debris field has been created, but it shouldn't be a threat to the ISS or the shuttle. However, it could cause problems for the rest of the Iridium satellites, since they are on similar orbits.
http://news.bbc.co.uk/2/hi/science/nature/7885051.stm
http://news.bbc.co.uk/2/hi/science/nature/7885051.stm