If you don’t know what a tumblelog is, read this:
A tumblelog is a variation of a blog that favors short-form, mixed-media posts over the longer editorial posts frequently associated with blogging. Common post formats found on tumblelogs include links, photos, quotes, dialogues, and video. Unlike blogs, tumblelogs are frequently used to share the author’s creations, discoveries, or experiences while providing little or no commentary. – Wikipedia
It is kind of like twitter, but in my opinion better. And it is because I think it is better that I think I will actually use it, unlike twitter.