Audio Test and Measurement for DIY

The information in these pages is mirrored from my Facebook group DIY: Audio test and measurement.
Just like many DIY audio enthusiasts, I'm unable to justify the cost of an Audio Precision analyser, or other dedicated audio test hardware such as Prism Sound dScope (now Spectral Measurement) etc. for use at home.
Therefore these pages are all about exploring the use of computer hardware & software along with a sound card or USB interface to perform accurate audio measurements.
The software is primarily targeted at Windows, as that's the platform most people use - however I am also exploring options for Linux.
I have successfully run Arta and WaveGene / WaveSpectra under Wine on Linux.