Adding a section where you can display links to certificates earned in online classes on sites such as Coursera, Udacity, edx, etc.
I don't really see the need to specifically single out a MOOC. There's already a section reserved for Certifications, and the entry is free-text. That is, since you are not prompted to select from a list of already existing certificates (like Stack Exchange tags, for example) you can type in any certificate you wish in that area.
Perhaps a better suggestion would be to simply add a hyperlink to the existing Certificate entry box for links relevant to the certificate.