+ del.icio.us plugin -- Add/remove/edit del.icio.us bookmarks from a right mouse click.
* Foxylicious -- grabs your del.icio.us bookmarks and adds them to your local Firefox bookmarks.
* sitebar plugin -- An alternative to del.icio.us. I started running a copy of the SiteBar server on my home Linux box, but it is just simpler to use del.icio.us and for private bookmarks to just keep it locally (internal corporate links, etc)
* webdeveloper plugin -- I don't use it much, but it is handy to find any links within a webpage.
* SwitchProxy tool -- switch proxies as needed. Useful when if you connect to various networks with different proxies settings.