Tumblr should be a part of every journalist's routine.
Of course while doing my daily scroll through my own Tumblr dashboard I found this particularly relevant post on markcoatney's Tumblr — a Reuters article describing the importance of Tumblr for journalists that explains why they should jump on board with this form of versatile social media.
As an avid Tumblr user, I can attest to it's innovation, particularly for journalists and news organizations. I follow several NPR Tumblrs (Fresh Air, NPR Music), the LA Times as well as various mainstream and amateur freelancers, bloggers and journalists (here are some good ones to check out, Soup and The Political Notebook). I find that many of these blogs utilize the multimedia aspect to the fullest, and in particular the "reblog" function, something the article mentioned as one of the most viral features of Tumblr. Although individuals who are reblogging aren't necessarily producing original content, they are significantly contributing to spreading news and information (as the article mentions, "it acts as a natural amplifier").
So if you're interested in jumping on Tumblr and exploring how other journalism outlets use it, NPR compiled a list of other public media Tumblrs worth looking at. It's the next big thing.