Even though most people use the computer for the vast bulk of office tasks these days, there are definitely times when a fax machine comes in handy. However, say you're at home and you need to send a fax. Do you have to find a fax machine? Pay outrageous fees at the local copy shop? If you're only sending a quick, one-time transmission, not necessarily.
Note: Most of these services offer a few free faxes initially, and then offer a paid service for further faxes. These sites are perfect for those times when you just need to send one or two faxes.
FaxZero gives you two free faxes a day, and if you are a very infrequent faxer (like me) than that's all you need. Simply save the document you're faxing onto your computer somewhere, provide the fax number and company information, and send the file; kind of like sending an email. You will receive a fax confirmation in your email inbox within 20 minutes if the fax was sent successfully.
ScanR is an intriguing service that turns your camera phone into a scanner, copy machine, and fax machine all in one fell swoop. Here's how ScanR works: basically, you take a picture of a document you want to share with someone else, send it to a ScanR email address, and they send this document on by fax as a .pdf file. You'll have to download the ScanR software to get the more detailed services, and you'll want to figure out which level of ScanR you'll want to subscribe to (basic services are free).
Pamfax is free to join, and new users get three free fax pages. Support for Dropbox, Box.net and Google Documents is built in to the service. If you decide to upgrade, PamFax will provide you with your own personal fax number.
MyFax will send one free fax for you to 41 different countries, and you'll get a confirmation email in your inbox once it's done. This one free fax can include up to ten pages.
Popfax is a fax service that offers a free fax online trial, but then goes to a paid subscription service. Popfax works very similarly to the other fax services detailed in this article with a few differences: it does offer worldwide fax service, and they keep your documents in storage for 30 days. The subscription fee is low enough that it's worth a look if you send more than 5 faxes a month.