Bad news: This was a nearer thing than initially realized, and assuming Discovery does reach the ground safely, it's likely to stay there for a long, long while.
On the off chance you've missed the news today: A piece of external-tank foam -- about the size of the chunk that ultimately killed Columbia -- broke off about two minutes into the launch. It didn't hit the shuttle, but had it broken off earlier, in heavier atmosphere, it probably would have and it probably would have had the same effect, leaving seven astronauts stranded on a space station designed to hold three (ignoring the two people already there, since they have a Soyuz to come back in) until NASA figured out a way to get them home, hoping that their one real option -- send another shuttle up -- didn't run into the same problem. NASA is now saying that the shuttle fleet will remain grounded until the problem they thought they'd solved with the external tank is actually solved.
Right now, I seriously doubt it's solvable.
Simply put, I am increasingly convinced that the problems with the external tank specifically and the broader problems with the Space Transportation System as a whole cannot be kludged out of existence, as NASA has been trying to do for a quarter-century now (longer if you count the design phase). I Am Not An Engineer, but I don't really see how you can be absolutely sure no foam will break off the ET under the stresses of launch. The problem is that the thing is covered in foam; modifying the bit that broke off last time while hoping the rest of it will simply stay put is a barn door/horse situation. And sheathing the foam in something would add too much weight for the shuttle to be much use in ferrying things up to the station, which is pretty much its only reason for existence now. (selenite? Gerry? Is there something I'm missing here?)
It seems to me that if NASA has decided no foam breakoff is acceptable, then the space shuttle is done. You'd have to completely redesign the tank, and the time and money that would take you might as well spend on the shuttle's replacement. If it's going to be that long until the next shuttle flight anyway, we'll probably have to abandon the space station, too, which I think is a pity. The alternative is for NASA to decide they're willing to roll the dice on the fuel tank and all the other things wrong with the STS.
But even then we need to get cracking now on the shuttle's replacement now. It may well be that NASA is no longer the answer, and I'll just have to put my faith in the America's Space Prize (aka the Bigelow Prize, the orbital successor to the sub-orbital X-Prize). (This also leaves open the question of heavy-lift capability, but that's another rant... tired now...)