Diarist is a Windows Mobile application that uses a cell phone's internet connection to communicate with your blogging service. Out of the box, Diarist is compatible with some of the most popular blogging platforms on the web including Wordpress, Live Spaces, Community Server, and pretty much anyone else that supports generic metaweblog APIs. The free software requires you to install the .NET Compact Framework which allows developers to basically develop once on the desktop and package for a mobile device.
Blogging on the road has been a huge productivity boost for me since I mostly use public transport in England. Anyone who is a serious blogger with a decent phone needs to download this app.
Anyways, I gotta run my train has just arrived at Paddington station. :)