[Update (14:00 Mountain time): The launch of the Shuttle has been postponed by a day due to a hydrogen leak. I'll have more, including an updated launch time, later.]
Two things, of opposite natures.
1) Debris from the smashed Cosmos satellite is predicted to start re-entering Earth's atmosphere as early as Thursday according to spaceweather.com. That's earlier than I expected, but not by much; I figured it would be a few weeks. Basically, debris that had orbits that dipped lower would get more drag from the Earth's very thin atmosphere at that height, and over time their orbit drops. As they drop, the air gets thicker, dropping them more, until... fzzzt! Evidently, for reasons unknown (I suspect collision geometry and the construction of the satellite itself -- it may have been internally pressurized) the debris cloud from the Cosmos satellite expanded more than from the Iridium bird, so it's coming in sooner.
2) The Space Shuttle is due to launch at 21:20 Eastern (US) time Wednesday night (01:20 UT Thursday morning). It'll be covered on NASA TV of course, and I expect I'll live tweet it. Damaris Sarria, an astronaut candidate, will be on various venues discussing it as well!
And since I know you're wondering... according to NASA, the debris poses a very small risk to the Shuttle over the usual background field of junk up there. Hopefully everything will go smoothly and safely.