Below are some useful measurement and analysis tools–with relevant descriptions–that can be found on the web. 


Acoustics Engineering (Sabin and Dirac): 
Developers of Sabin andt Dirac acoustical software


Brüel & Kjær: 
Measurement microphones, sound level meters, analyzers etc.


Davis Instruments: 
Test Instruments for Industrial Applications


DRA Laboratories: 
Developers of MLSSA acoustical measurement system


Gold Line: 
Manufacturer of numerous audio / acoustical measurement devices plus owner of the TEF line of acoustical analyzers


Integral Acoustics: 
Manufacturers of some neat little software products for various acoustical and electroacoustical applications – some of them freeware


LARA: 
Loudspeaker Acoustical Room Analyzer (LARA)


Larson Davis Inc.: 
Manufacturers of noise dosimeters, sound level meters etc.


Liberty Instruments Home Page: 
Developers of the IMP, IMP/M and Liberty Audiosuite audio analysis systems for loudspeaker and electronics designers


LinearX: 
Manufacturers of the LMS Loudspeaker Measurement System software


Ptolemy Services: 
Developers of Jade environmental noise monitoring and dataloging software


Pure Bits: 
Manufacturers of “Sample Champion Version 2.0” – very nice acoustical analysis software with surprising functionality. They also offer some really neat downloadable wallpapers (free)


RPG Diffusor Systems, Inc.: 
Great source for acoustics background information. Developers of RPG Room Optimizer software


SIA Software Company, Inc.: 
Developers of SIA Smaart (formerly known as JBL Smaart) acoustical measurement and analysis system


Sound Technology – Spectra pcSeries Softest: 
PC-based test, signal processing, data acquisition and instrumentation software


Terrasonde: 
Manufacturer of the Audio Toolbox – nice low-budget measurement tool


Test and Measurement: 
Virtual community for the test and measurement industry


The Speaker Building Page: 
Interesting acoustical shareware and freeware programs


Sound Devices: 
Manufacturer of a portable USB audio interface with built-in 24 bit A/D converter and +48V phantom power – powered by the USB port! Perfect companion for many audio / acoustical measurement software packages


WinMLS: 
Windows-based MLS measurement software