I posted this earlier under another thread, but it perhaps rates its own, so here goes.
Angstrom Loudspeakers
http://www.angstromloudspeakers.com/

Athena Technologies
http://www.athenaspeakers.com/

Axiom Audio
http://www.axiomaudio.com/

Coincident Speaker Technology
http://www.coincidentspeaker.com/

Dahlquist
http://www.dahlquistcorporation.com/

Energy Loudspeakers
http://www.energy-speakers.com/

Ethera
http://www.ethera.com/

Fidelity Acoustics
http://www.fidelityacoustics.com/

Focus Audio
http://www.focusaudio.ca/

Gershman Acoustics
http://www.gershmanacoustics.com/

Hemp Acoustics
http://www.hempacoustics.com/

Lightning Sound
http://www.lightningsound.net/

Mirage Loudspeakers
http://www.miragespeakers.com/

New Form Research
http://www.newformresearch.com/

Paradigm
http://www.paradigm.ca/

Pro-Linear Electronics
http://www.pro-linear.com/

PSB Speakers
http://www.psbspeakers.com/

Quest
http://www.questhifi.com/

Reference 3A Loudspeakers
http://www.reference3a.com/

Sinclair Audio
http://www.sinclairaudio.com/

StudioLAB
http://www.speakerdirect.com/

Tetraspeakers
http://www.tetraspeakers.com/

Totem Acoustic
http://www.totemacoustic.com/

Verity Audio
http://www.verityaudio.com/
Note: I don't guarantee the list is complete -- sorry if I missed anyone. Let me know if so. All links are up to date to my knowledge, again, e&oe. Many thanks to those who contributed makers I missed.