The new release of WordPress (version 2.6) is due in August 2008 and is compatible with Google Gears.
*this refers to self hosted WordPress software, not the wordpress.com blogging platform.
Unlike Google Reader or Google Docs where Google Gears helps you work in an offline environment, WordPress is using Google Gears for a completely different purpose and that is to speed-up your regular blogging tasks.
With Google Gears, WordPress will store all these ‘static’ files on your local hard drive and will not download them from the web server each time you perform some action in your WordPress admin interface. Thus, it should speed up things especially if you are on a slow connection.
I don’t think you can blog offline with WordPress 2.6 like creating new posts or moderating comments. For more technical details about Google Gears support in WordPress, check this support ticket.
Also see this full list of Google Gears compatible web applications.