FaxZero is a service that allows you to send a free fax, anywhere in the US or Canada, from your computer.
You simply enter your info and the recipient's and then upload a file (.DOC, .DOCX, or PDF). The service then sends you a confirmation email. Click on the link and it will send your fax. You will get another email when the fax has gone through successfully (or failed).
Free faxes are limited - ad on the cover page, 2 free faxes per day, limit 3 pages per document/fax. You can page $1.99 for a fax with no ads and a 15 page limit and get priority over free faxes. You can also pay for international faxing. It usually takes 5-10 minutes for the fax to go through. Faxes to Japan are free right now.
This comes in really handy when you have to fax something and the school fax machine is down, or completely across the building, or when you are trying to be paperless.