Here's what I know off the top of my head, but I'm sure I'm missing several. Chime in if you know others.

I'll be bringing a pair of four π's this year with JBL 2226, B&C DE250 and top-of-the-line crossovers.

Keith Larson of Smith and Larson Audio will be bringing his latest testers and will be doing a seminar on electro-mechanical and acoustic measurements.

Bob Brines will be bringing his latest and greatest stuff and will be doing a presentation on quarter-wave pipes.

Element Cable will be there.

Duke LeJeune of AudioKinesis will be bringing his speakers, and if I remember, he has something new.

Great Plains Audio is bringing some of their stuff.

MaxxHorn is going to be there with their speakers.

SoundStage! will be there.

I know I'm forgetting a lot of vendors and equipment. Please forgive my omissions and add to the list.