Her resignation letter cites Senate demands for release of internal White House documents in advance of her confirmation hearings - the Krauthammer Exit Strategy. Personally, I'm glad she has done so but I didn't exactly oppose her nomination. How's that for straddling the fence?
Commentary from elsewhere, including speculation on the next nominee:
Althouse, Althouse, Althouse
Hugh Hewitt
The Anchoress - hmm... was she prescient?
Gateway Pundit
Daily Kos
Wizbang
Volokh Conspiracy
Tigerhawk - brilliant suggestion!
TPMCafe
Captain's Quarters
Southern Appeal
Classical Values
Garfield Ridge
My Vast Right Wing Conspiracy
Outside the Beltway - good McConnell bio
Patterico
and probably everybody else too.