SRFax lets you send faxes via e-mail or the web, and provides a toll-free phone number for incoming faxes.
SRFax Prices
Citywide Lite plan: send/receive a total of 200 pages per month for $9.95 a month
Citywide Business plan: 400 total pages for $15.95/month.
There's a free 14-day trial, and discounted annual rates are avaiable. Several e-mail addresses can be authoized to send faxes: 3 for the Lite plan, 9 for the Business plan.