I'm going to be really honest about this one: I had no idea that anyone still uses LiveJournal. Much to my surprise, though, it has been going strong all this time - it's even ranked #71 in the world according to Alexa. After realizing that tidbit of information, it's not surprising at all that there is now an official LiveJournal App for Android.
For a mobile blogging app, I must say that this one seems quite feature rich: you can post new journal entries and photos, create polls, edit entries, create drafts, and manage settings. From just a quick look, I think that this may be the best on-the-go blogging app that I've seen thus far.
I would say that this is a must have app for everyone that uses LJ, even the most casual user. You can grab it for free in the Android Market.