Associations  

ASCAP

Audio Engineering Society  

SPARS

Audio Sites & Blogs:

Behind the Mixer 

Dave Rat Blog

Digido - Audio FAQ

Doctor ProAudio 

FOH Online

Free Loops

Lighting and Sound America

Massive Mastering - Blog

Media College

Mix Magazine

Music 3.0

Pro Audio Files 

Pro Sound Web 

Production Expert

Production Advice

Rational Acoustics 

Shaking Through - multitracks

SynAudCon

Tape Op Magazine

The Physics of Sound

UA Blog 

Manufacturers:

Avid 

Lavry

Meyer Sound 

Shure

Waves

Online Calculators and Tools:

Acoustic and Vibration Animations

Audio Calculators

Audio Check.net

Paul Falstad - Tons of audio & physics applets!

Metronome Online

Studio and Audio Calculations

Smart People:

Bob McCarthy

Dave Rat

Ethan Winer

Michael Curtis

Leslie Ann Jones

Manny Marroquin

Michael Brauer

Pro Audio Resources