Update: Since Tumblr removed the embed code from its "Goodies" section, Adriel discussed this topic on a recent episode of NationBuilder Live. You can see the clip and learn how to add Tumblr to your website in a newer blog post.
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Lots of nationbuilders have been asking about adding aggregated content to their nations. One really easy way to do this is by adding Tumblr to your nation.
Tumblr allows easy sharing of media, links and short blog posts. The microblogging site is one of the fastest-growing on the Internet and is highly social. It also makes it really easy to grab an embed code.
To add Tumblr to your nation, get your embed code from Tumblr by logging into your account there, going to the bottom of the page and clicking "Goodies" then grabbing the embed code from the field on the lower right of the page.
Go to your nation dashboard, click on Websites > New Page and pick the "Basic" page type. Create your page and go to the template and paste your embed code between the first pair of </div> tags. Save and publish and you've got it.