Yes, every now and then they run a free shipping day for purchases of $50 and up. There was one just a week or two ago. But there is no set date, and they don't say when it is, so you have to log in every day and check.
You can sign up for daily "deal of the day" emails also - and so when free shipping is the deal of the day you'll get it right in your inbox. (Also, follow on facebook/twitter.) The deal of the day link is in the upper left corner of this screen - from that link you can sign up for the emails.