Best blog post I've seen so far is from Talkingpointsmemo. Judith Miller's former attorney says Miller essentially could only have heard the name "Valerie Flame" from Scooter Libby, Karl Rove's aide. Miller meanwhile says she didn't think she got the name from Libby, and did discuss the Plame issue with other sources, but can't remember who or when.
My interpretation is that she wanted to sing herself out of jail while lying enough to keep from putting Libby in jail. It would be very hard for a jury to convict Libby for revealing Valerie Plame's name to Miller, based on Miller's testimony alone. But if Libby cracks someday under pressure and tells the truth, it would also be hard to convict Miller of perjury since she didn't say she was certain it wasn't him. Trying to prove a negative - that her other sources whose identity she can't remember - is nearly impossible. Assuming Miller doesn't actually care about Libby, we can conclude she's doing this to remain a player in national security news. The motive can't be journalist ethics, since she is presumably lying her head off.
There are three flaws in Miller's plan. First, she's not the only one supplying evidence against Libby, so her attempt to degrade her evidence does not completely eliminate its usefulness to the prosecution when added to whatever else they're presenting. Second, the name may not matter - outing a now-identifiable covert CIA agent is enough to break the law. Third, Miller will face repurcussions outside of court, where a strong suspicion that she's a dirty liar should be enough to put a well-deserved dent in her career.
So what's with her former attorney, Floyd Abrams, spilling the beans? Attorney-client privileged information can be released only at the permission of the client. Assuming Miller didn't give permission, Abrams may have just screwed up and said far more than he should have. Alternatively though, he may have previously told the prosecutors (or the judge? not sure if they had any closed sessions) that there was only one source. If Miller then changed her tune, with the effect of making Abrams look like he lied, then he has a lot more room for disclosure in order to protect himself.
We'll see the real opening salvos for this, really soon.