Have multiple accounts I recommend this plugin:
mozdev.org - cookieswap: index
1 click and you can change cookies so no need to log in each time with your other accounts
The web developer toolbar, thats one of my favourites, I also really like the HTML validator addon, those coupled with Firebug and your FF is perfect for web dev. I might try that SenSEO myself, sounds quite good.
Useful FireFox Addons :
- Web Of Trust -
- Tab Kit
- Deng Google Bookmarks
Pixlr Grabber (grab, edit, share, save or copy images) : https://addons.mozilla.org/en-US/firefox/addon/9924/
Now that site speed is a ranking factor with Google, don't forget about YSlow. It works with FireBug and is good for finding ways to speed up your sites. I cut the loading time in half for some of my sites by following the YSlow advice.
Yahoo! YSlow for Firebug
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin