Check out Tumblr, a new service for sharing and self expression. Whereas Twitter lets you tell everyone what you are up to, Tumblr provides and easy way to share “experiences.”

Union Square Ventures, the company that is financing Tumblr, also explains it this way:

At Flickr the atomic element is the image, at YouTube the atomic element is the video. By contrast, at Tumblr the atomic element is whatever works best for you now. Really into a Feist song right now? Can’t stop watching the video of a dramatic chipmunk? Want to rebut a NY Times Op-Ed? Just toss it up on Tumblr. And all types of media are handled correctly and presented elegantly, because your personal expression is a representation of you, so it should look good.

They add:

Self-expression means different things to different people, so Tumblr is flexible to all those definitions. I’ve seen many interesting use cases for Tumblr over the past few months: Steve Rubel uses Tumblr to aggregate his shards of web presence into a single lifestream. Steve Ruble has a blog, and uses Tumblr to supplement his blogging. Jake Jarvis aggregates many of this services through Tumblr too, but Jake doesn’t have a blog in addition. Tumblr is his blog replacement. Some Tumblr pagers look like photo blogs. Others are a mash of everything imaginable. I like the idea that Tumblr is what people make of it, and so I appreciate the wide range of use cases.

For more information, there’s a good article and podcast on Read, Write, Web.