Measuring Audio Latency
A few links about measuring audio latency on Windows, Linux, and Wine.
Audio Latency Measurement Howtos and Results Pages
https://ccrma.stanford.edu/~matt/latencytest/ - "Latency testing of gesture triggering of synthesized sound", 2004, Matt Wright
http://www.soundonsound.com/sos/sep02/articles/pcmusician0902.asp - "THE TRUTH ABOUT LATENCY: Soft Synth Latency And Latency Jitter: Real-world Tests", 2002, Sound on Sound Magazine
http://www.music.mcgill.ca/~ich/research/icmc01/latency-icmc2001.pdf - "Audio Latency Measurements of Desktop Operating Systems", 2001, Karl MacMillan (Peabody Institute Of The Johns Hopkins University)
http://linuxdevcenter.com/pub/a/linux/2000/11/17/low_latency.html - "Low Latency in the Linux Kernel", 2000, Dave Phillips
http://manual.audacityteam.org/index.php?title=Latency_Test Audacity manual - how to test and compensate for latency using Audacity
Automated Audio Latency Test Tools
Listed by platform and API. (I can't find a generic tool that supports multiple platforms and APIs. Know of one? Please write dank at kegel.com)
linux alsa: http://alsa-project.org/alsa-doc/alsa-lib/_2test_2latency_8c-example.html - Jaroslav Kysela's latency test, part of alsa-lib. (Fails for me on Ubuntu 9.10 with an error like https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1827 )
linux alsa: alsa-time-test (see http://www.pulseaudio.org/wiki/BrokenSoundDrivers )
linux alsa: alsa-latency (demo app in libclalsadrv-2.0.0, see http://www.kokkinizita.net/linuxaudio/downloads/clalsadrv-2.0.0.tar.bz2 and fons@kokkinizita.net's post of 14 Mar 2010 to http://lalists.stanford.edu/lad/2010/03/ )
linux jack: http://www.kokkinizita.net/linuxaudio/downloads/index.html - jack_delay, an old latency test
Win32 ASIO: http://www.centrance.com/downloads/ltu/ - Centrance latency test tool (See also Tom's Hardware results)
Win32 DirectSound: http://www.guitar-fxbox.com/sctest.htm (outdated)
Scheduling Latency Test Tools
These just measure operating system scheduling latency, and aren't audio specific.
win32: http://www.thesycon.de/eng/latency_check.shtml - DPC Latency Check
Midi latency test tools
These aren't about audio latency per se, but about midi message processing latency.
linux alsa: http://github.com/koppi/alsa-midi-latency-test
win32: http://earthvegaconnection.com/evc/products/miditest/index.html
Notes
http://pulseaudio.org/wiki/PerfectSetup says "If a gamer wants lowest possible latency, and does not need any other app to play sound (like voice chats like "Teamspeak"), then they should use pasuspender. This makes PulseAudio release the hardware interface, so a game can use it exclusively, and without dmix or PulseAudio in between." So any latency measurements should be repeated both with and without pasuspender.
http://proaudio.tuxfamily.org/wiki/index.php?title=PulseAudio seems to describe using Pulseaudio on gentoo with Jack applications, and says "I was able to get PulseAudio to be 100% stable only with a 42.7 msec JACK latency."
http://benheck.com/for-sale is a gadget that lets you measure game-controller-to-video latency. Not at all related to audio, but still interesting.