In terms of classroom application, Tumblr would be a good way for you to share research for projects and assignments. Your students could then follow your Tumblr site and ‘reblog’ items into their personal site.
Or you could have students create multimedia (photos, videos, etc.) and post them onto their Tumblr. Then you could see how many views, likes, and reblogs each one gets. Could be a great way to encourage social media usage in schools using a free web 2.0 tool.
Finally, you could use it to connect with other teachers and education professionals. After just a few Tumblr searches and posts, you’ll find that people start coming out of the woodwork to ‘like’ your content and share it. You can quickly find fellow teachers and education-y folks by simply searching keywords like ‘teacher’ ‘edtech’ and so forth. When you find some good content, be sure to like it and reblog it. That person will then check your site out, start following your Tumblr, etc. Before you know it, you’ll have a whole new PLN on Tumblr!