I've come across a couple of new, simple to use, almost throw away blogging tools recently:
Throwww
Throwww is the easiest way to write something and share it. Just start writing, post it, and share the url. Posts on Throww can be tied to your twitter account, as my examples, or anonymous.
Authpad
Authpad (beta) is a frictionless approach to blogging. Our goal is to take away any distraction that keeps you from focusing on what's important -- producing quality content. Authpad has more of a traditional username/password setup, comments via disqus and themes.
Both support markdown for writing and work on iOS (I tested with an iPad).
Both also get away from the relative complexity of most blogging platform's 'dashboards' and editors. Authpad has a slightly less minimal editor, as it has a toolbar:
Whereas with throwww you just type on the home page. Once you type a bit the save button and a Formatting Help link show up, which will give you markdown help.