WriteToMyBlog currently in beta is a free web based word processor (blog editor) for your blog, that let users write & publish post without logging into their blog editor panel. You can also post the same blog posts to different blogging platform upto 3 blog accounts max. WriteToMyBlog also comes with spell checker, which is a must tool for every bloggers.
The editor support WordPress.com, WordPress.org, Blogger.com(BlogSpot.com), TypePad, Movable Type, and DotClear blogging platform and at the browser front, it work with Microsoft Internet Explorer or Mozilla Firefox.
Alos read Offline Blog Editors desktop clients, which work right from your desktop like Word, Notepad.