Granted, e-mailing someone an attachment is not difficult. Neither is sharing files via Dropbox, Google Drive, or another online repository. If you use a Mac and are on Facebook, however, there is an easier way. Free app SendRail makes sending a file to your Facebook contacts just a right-click or keyboard shortcut away.
After installing SendRail and hooking it into Facebook, you will hardly know it's there. It adds a small icon to the menu bar, along with a line to your right-click menu. To send a file via SendRail, right-click on the file and choose "Send To Friend Via SendRail" or highlight the file and hit Command-U. Either action calls up a small window in which you can enter a contact name and send the file. SendRail uses autocomplete in this window, but only as long as you use proper capitalization.
A recipient will receive a Facebook message with a link to open the file; he or she does not need to have SendRail installed. SendRail uses 256-bit AES encryption to protect your file transfers.
I did not test it, but SendRail claims that two SendRail users can send files via a direct, peer-to-peer connection, leaving SendRail's servers out of the equation.
SendRail also states there is no limit to the size of files you can send. In my tests, text documents and photos arrived quickly, while larger video files took longer. You can also send multiple files and entire folders via SendRail as well. You can't, however, send a file to more than one contact at a time.
SendRail's design is almost too simple. You, the sender, for example, receive no verification that a file successfully made it to its intended target. There is no status window while the file transfers, and there is no option to copy yourself. The only way to verify that a file went through is to go to the SendRail Web site and view the My Files page, where you'll see two lists: files you've sent and those you've received.
Also on the SendRail Web site is a way to connect to your Facebook friends, which seems to entail sending a message to two dozen or so randomly selected contacts. I found no way to add or remove names from this list. Thankfully, you don't need to complete this step to start using SendRail; I am able to send files via SendRail to any of my Facebook contacts. After you send this Facebook blast or cancel it, SendRail then mysteriously uncovers an offer to import your Gmail contacts. Alas, this Gmail option did not work for me.
SendRail works with Mac OS X 10.7 or later. Below is a video from SendRail, showing how the service works.