It appears that the nominee will be Judge Edith Brown Clement of the Fith Circuit Court of Appeals.
Here is some of the speculation:
Speculation Centers on Clement for Court - WaPost
A Tale of Two Ediths - National Review Online (NRO)
The Note - ABC News
Sources: Court choice could come Tuesday - CNN
Here is some info on Judge Clement:
Confirm Them (a conservative site tracking the nomination)
Daily KOS bio
People for the American Way commentary
Supreme Court Nomination blog's profile (from SCOTUSblog)
Edith Clement Resources (from Supreme Court Nomination blog)
The site above includes a couple of the sites I had linked, but also the following:
We'll see what happens today...
UPDATE I: Jurist - Paper Chase is reporting that Bush will announce the nomination at 9:00 pm tonight (EST - 8:00 pm CST)
UPDATE II: It's as official as it will get before 8:00 pm tonight - Sec. Specter's Staff Just Sent This Note Around The Senate
UPDATE III: Rather suddenly this afternoon, there is a lot of speculation that it will NOT be Judge Clement annoucned tonight. ConfirmThem (a conservative nomination blog) is saying that it is a bait-and-switch pulled by the Bush admin, and the real announcement will be of Edith Jones (also of the 5th Circuit). Judging the Future notes that Judge Michael Luttig (of the 4th Circuit) has his entire family with him at the court today...so it is really still up in the air. ABC News is now reporting that Judge Clement is NOT the choice...
"The October 4, 2001 confirmation hearing for Edith Clement is available full text online. See S.Hrg. 107-584, Pt. 1 on GPO access [here] . This includes submissions to the record, any follow-up questions, and her questionnaire."
We'll see what happens tonight...