AS Evan Sims mentions on his blog today, Automattic has released a version of WordPress for the iPhone (a client to connect to your remote blogging system).
There are a least a half dozen plugins for creating a more hospitable environment for managing your content on the iPhone, but quite honestly the quality of the ones I'd tried left a lot to be desired.
He noes that the application is "polished, official and completely native" and includes features that allow you to take a picture with the phone's camera and embed it directly into the post you're writing. Check out the sample video of it in action on an iPhone. You can download it from the App Store for free.