I've been using Send2Fax (send2fax.com) for a couple years, and I'm quite happy with it. $11.95/mo and includes a toll free number. Don't know off hand if there is a page limit, but I've never been charged anything extra. I got it primarily to be able to get FAXes by email.
To send a FAX you login to your account, type in the number (or get it from your address book that you've saved), upload the file to send, select the cover sheet if desired and fill it out, and click send. They email you a confirmation once it's sent. All the standard file formats are supported. Incoming FAXes come to your email address as a PDF, and can be viewed online as well.
Be ware it you use this kind of service with sensitive data (such as credit card numbers). It's no more secure than the email.
The concept of 'bogus' FAXes, as noted in an earlier post, is not quite correct. The FAX service has no way of screening them. Maybe they can block incoming numbers, but that would be it. If someone sends you an unsolicited FAX there are substantial penalties, and there are companies that will hunt these people down to stop them, and some even pay you a portion of the 'fine' they get. Check out this site to learn more on this:
http://www.faxrecoverysystems.com/identi-fax-center.asp (no affiliation or recommendation inferred, just an FYI)
John