Embarassingly, I never used IA32 before coming to Intel. Now, I have Intel's IA32 reference, and a big fat reference it is. It has lots of chunky tables about instruction encoding and opcode formats. It is a reference, though, and not an introduction or tutorial. I'm looking for something probably on a 213 level or so, but hey, post what you got.
I am spending lots of time in the past month looking at pipetraces and it would be smart if I had some more grounding in IA32 assembly.