I love Windows Live Writer for blog editing. But if I'm in Mac OS, firing up VMware just to run it seems like overkill. I used to use ecto as a blog editor but not only has it not kept up, it never really worked well for images.
Enter Blogo, featuring ease of use and a minimalist UI, it might fit the bill. It supports a large number of blog services out of the box and adds microblogging support for Twitter, and anything that is on ping.fm.
For those who like a full screen approach to editing their blog, Blogo's full screen editor almost delivers the goods. You're edit window is the middle third of the screen, but the pleasing grey background removes most distractions.