Serious bloggers might want to check out Blog Desk. It is a totally free application for WordPress (and other less popular blogging systems). A key feature for me is the ability to cross post to multiple blogs.
Blog Desk works with Windows 98, NT, 2000, ME, XP, Vista and 7. The interface is very simple. I find it easy to work with, particularly when it comes to images. However, I think the best feature is the cross posting ability. Blog Desk can post to multiple blogs easily once it has been set up.
The interface is spartan but has the features that I need to share my opinions, views and topics of interest with the world. Good stuff. If you are serious about putting out a lot of content across multiple blogs you should check out Blog Desk. Be sure to read the frequently asked questions as some of the more useful features do not necessarily jump out and beg a blogger to use them.