Literally fantastic.

Quoted: ROYAL DEVICE are audiophile quality speaker systems,the BIGGEST SPEAKER of the WORLD and The biggest Horn SUBWOOFER of the WORLD for GREATEST AUDIO ROOM of the WORLD, Featuring new, superb design and outstanding performances, built with the best materials, custom components and drivers, precious wood and state-of-the-art finishing

Oscilloscope, spectrum analyzer, FM AF signal generator, AF noise generator

Nice set of texts on basic sound construction offered free online.

PAiA FatMan built into an old briefcase with killer accents.

Cool web tool for filter calculations

Quoted: Sallen Key Low Pass Butterworth Filter Calculator.

Quoted: A strongly-timed, concurrent, and on-the-fly audio programming language

Small, portable panels for attenuation & partial isolation in studio. Framed & enclosed fiberglass batts.

Ready Acoustics also offers free advice as a form of pre-sales customer service. One of their (inexpensive, less than $100) services is 3D modeling of your home theater.

Wonderful set of MP3 audio samples: Shepard's Ascending Tones, Falling Bells, and Quickening Beat.
Each link takes you to an external website, below the embedded player there is a box with a text link to "DOWNLOAD THIS FILE". You can't get the effects unless you download the MP3s and play them in loop mode on your own system.