Blog it from Windows Live Writer. Windows Live Writer is a new desktop application for composing blog posts to your blog service.
Currently the addon posts a page link or selected text to Windows Live Writer. You can access it from the context (right click) menu or the main menu. To use it you need to have Windows Live Writer installed on your machine.
Download Firefox Extension
Currently it is pending for aproval on firefox site, you can download from the link below.
It is now available on firefox site as well.
From my Site
Install Live Writerfox
v0.5 (2010-01-18) Firefox 3.6 Support
v0.4 (2008-06-21) Firefox 3.0 Support
v0.3 (2006-10-25) Added Firefox 2.0 Support
v0.2 (2006-08-27) Added toolbar button Blog It URL issue has been fixed Removed extra double-quotes
v0.1 (2006-08-19) - Initial Stable Version. Blog a page. Blog selected text.