You may have come across several web based faxing services that let you send faxes over the Internet for free but they all impose certain limitations.
For instance, they may not let you fax more than two pages at once or may add advertisements in the fax cover sheet or may not support rich text documents.
drop.io (pronounced as "drop-ee-o") overcomes all such problems and lets you fax Word documents, PDF files and even Excel a spreadsheet via Internet to any phone number in the United States for free.
You can send unlimited number of faxes without registration, there are no ads attached to the fax sheets and each fax document can have up to 20 pages.
To send a fax, just upload the document (or PDF) to drop.io and click the "Drop It" button. On the next screen, click the ’send as fax’ near your document and enter the 10 digit fax number of the recipient. Hit Send and your fax will be printed on the recipient’s fax machine in few minutes.