Besides Proakis and Manolakis, which I wish I had found when I was
starting out in DSP.

Fundamental of Statistical Signal Processing, Steven M.Kay
-Vol 1: Estimation Theory
-Vol 2: Detection Theory

Signal Theory and Random Processes, Harry Urkowitz

Not strictly a book, but a good CD (pdf) reference:
DSPedia: An A to Z of DSP, Bob Stewart