The second you publish a new post on WordPress.com, you can instantly share it on Facebook, Twitter, Yahoo, LinkedIn, and now Tumblr with a feature called Publicize. This helps you get exposure to multiple audiences without having to manually share your content on all your favorite social sites.
With Publicize, you can make WordPress.com your home on the web and automatically share your content on five other social platforms. By publishing to WordPress.com, you maintain ownership of your content, which you can choose to export at any time. After you have connected, your new posts will be shared on Tumblr and no other action is needed.