I got a Eye-Fi Wifi SD Card for Christmas. It works great on my Canon 5d3 and gives me the wifi uploading that Canon should have baked in from the start (they added it into the cheaper 6d, ugh!). It can upload to a number of online services, including Facebook. I set it up and had it working for the first few uploads, but after that it stopped posting to Facebook. Everything showed up fine in the online Eye-Fi gallery, but nothing went to Facebook.
They are a couple of things you might have to check to get it working. First, make sure the privacy/sharing for the album you are uploading to is set to atleast Friends. Also check the Album, I had a bunch of photos I had to “Approve” because they were uploaded by an App. Hopefully that goes away after I approve it a couple of times. Then goto your settings, then Apps, and then the Eye-Fi App and make sure its privacy/sharing is set to atleast Friends.
It is working flawlessly and it is so cool to be able to hit one button on my DSLR and have it automatically post to Facebook. It is even easier that on the iPhone. I remapped the Rating button to be Protect in order it make it super easy.