MarsEdit - MarsEdit is a desktop blog editing application for the Mac. It provides an offline interface to most popular blogging systems. WordPress, Blogger, Tumblr, Movable Type, and many other systems are supported.
ZenPen - A minimalist writing zone, where you can block out all distractions and get to what's important.
BlogDesk - Blogging should be simple, but it gets complicated and time-consuming if you are serious about it.
Telescope - Telescope is an open-source app that lets you easily set up your own online community.
Open Live Writer - Open Live Writer makes it easy to write, preview, and post to your blog.
Typefully - Write & publish great tweets, without distractions