A tumblelog (also known as a tlog or tumblog) 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.
Blogging has mutated into simpler forms (specifically, link- and mob- and aud- and vid- variant), but I don’t think I’ve seen a blog like Chris Neukirchen’s Anarchaia, which fudges together a bunch of disparate forms of citation (links, quotes, flickrings) into a very long and narrow and distracted tumblelog.
A tumblelog is a quick and dirty stream of consciousness, a bit like a remaindered links style linklog but with more than just links. They remind me of an older style of blogging, back when people did sites by hand, before Movable Type made post titles all but mandatory, blog entries turned into short magazine articles, and posts belonged to a conversation distributed throughout the entire blogosphere. Robot Wisdom and Bifurcated Rivets are two older style weblogs that feel very much like these tumblelogs with minimal commentary, little cross-blog chatter, the barest whiff of a finished published work, almost pure editing...really just a way to quickly publish the "stuff" that you run across every day on the web