One of the first apps I wanted to get on an iPhone was one to let me post into my blog. And the first one I have installed and took for the spin was BlogWriter. It is a decent application but I have very soon discovered that it is too basic.
This may be a function of my Blogger setup -- I have disabled automatic formating -- but creating a longer post has proven to be a challenge.
But more importantly it allows one to post to one blog only.
My next stop was iBlogger. The app does have a more polished and overall nicer touch and feel, supports multiple blogging platforms (except LiveJournal). Unlike BlogWriter it does insert a few tags on its own (line breaks, mostly), but it cannot save drafts on a server and does not allow to edit published posts.
The next (and last) application I took for a spin was LiveJiurnal.app. It supports only LJ for publishing, but where it shines is in quasi-rich editing capabilities that do not require constant switching between letters and symbols to insert HTML tags.
Mobile Blogging from here.