(I’m a Mac user; for Windows, check out something like BlogDesk)

I use WordPress…

• MarsEdit - comprehensive features, but no WYSIWYG editor.
• ecto - comprenhesive features, basic WYSIWYG editor. UI quite cluttered; not v pretty. Blog feature support the most comprehensive - will even handle password protection on posts. List of cools features here
• Blogo - slick, simple, great looking UI. Doesn’t seem to work v well offline as it doesn’t cache posts locally. Will preview your blog offline. But, WYSIWYG editor can overwrite styles it doesn’t recognise in posts. I’m currently trying this out.
• Qumana - free, but useless. Won’t recognise Extended part of post.

Useful overview here.
Reasons why not Ecto here. Personally I’m finding that it adds

tags to the summary, which forces the Read More.. link onto a new line…which is precisely what I don’t want. I’ve yet to find a workaround (I’m hoping there’s a template file I can hack).