Ah, a new extension for Firefox. This one allows me to post sites here using the sidebar instead of the link on my toolbar. I like this better than the built-in WordPress tool/URL that I used in my link bar since that tool pushed you to the posting page, then back to the source page. This made it impossible to reference the source page without opening a second window. Now I can type my post in the sidebar while reading the original page in the main pane. Excellent.
Thanks go to James who posted this story on his blog and to zilch_space who provided the fix that I was pointed to the wrong URL for the extension.