Twitter-esque thingy in Django, stores data on TypePad.

Send a link to your last published piece to SixApart, and they'll give you a free TypePad account, and enrol you in their advertising programme

Actually, it sounds like Lifeblog will support ATOM, which isn't exactly the same thing. (Moot for me for now - there's no Mac version of Lifeblog - and Windows types are presumably already using Lifeblogger to post via the MetaWeblog API)