I've just released a beta version of a desktop tool called UseShots Editor.
It's a free specialized program that will help bloggers take screenshots, annotate them and instantly publish on their blogs.
Here is the introduction:
http://blog.useshots.com/2008/02/29/screen-shots-for-blogs-meet-the-useshots/
Tutorial: Getting Started with UseShots Editor
(Created and published using UseShots Editor)
Current version works with WordPress' blogs only (both self-hosted and Wordpress.com-hosted).