If you can't be shagged to write a whole blog and feel that Twitter is too short - then tumblr's for you. You can also have your cake and eat it cos you can bang on longer at Typepad/Wordpess/Blogger and RSS it into your tumblr page - while simultaneously zapping your tumblr feeds off to Twitter.
It looks like tumblr want to position themselves as the blog/tweet/posting hub for your life. If they add universal IM as well - they could be onto one. Oh and check mother ship's tumblr page - click this link.