I'm actually writing this in Scribefire but it's promoting Windows Live Writer. Both are top notch tools for blogging. Scribefire sits in your browser and makes it so simple to blog as you surf, even letting you drag and drop images into your post. It's really my workhorse for blogging.
However I wanted a full featured desktop writer for more advanced post composition. I test drove a bunch and Windows Live is by far my favorite. Plus it's free (and better than some of the pay for writers). I'm managing three blogs (technically four since the comics page is actually another WP install). So these tools make life a lot easier.
And on the managing blogs note, I've revamped my oldest site, absenceoflight. Check it out!