I've been using an app called "Write" to experiment with a blogging platform called "Letterpress". Write is available for OS X on the desktop, but also as an iPhone and iPad app, so it allows me to update my blog using those devices. They all share the same dropbox folder, and Letterpress updates itself from the documents it finds in that same folder whenever new documents appear, or those documents change.
Write uses a Markup Language called "Markdown" which was created by John Gruber who also created the technology blog, Daring Fireball. The markup language lets the user create documents with annotations that are easily convertible to HTML. It is, in other words, well suited to blogging.
This very post was created using markdown and the "Write" app on my iPad.