From: http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00259105&lc=en&cc=us&product=2512008&rule=4965&dlc=

Send a one page black and white text fax to 1-888-hpfaxme (1-888-473-2963).

From: http://www.usa.canon.com/CUSA/assets/app/pdf/support/testing-your-fax-machine.pdf

Send a test fax to 1‐855‐FX‐CANON (1‐855‐392‐2666)

Note: MyFax.com

From: http://faxtoy.net/

Fax something interesting toll free to 1-855-330-1239 or 1-213-294-2943