Social media isn't just for celebrities who insist on Instagramming every aspect of their lives. It can be a powerful professional development tool as well. Here are some of my current favorite resources:
Twitter - I confess I don't check it regularly, but it is a great tool for professional development. Check out #tlchat, #libchat, #yalit, #edtechchat, #edtech, and more that I linked on my resources site.
Shelf Awareness - A daily email with news on publishers, independent booksellers, new titles, author book tours & television appearances, and trivia.
Book Bub - A daily email that lists the free and discounted ebooks of the day from Amazon, Barnes & Noble and others.
Google+ - Similar to Facebook, but seems to have more of a professional slant. Some of my favorite communities are InfoLit & Tech (my own) and Instructional Technology Integrators.
Listservs: An oldie but a goodie, listservs are still going strong. Some of my favorites are LM_NET, too many from ALA related to all aspects of librarianship, and the PA Schools listserv.