I have these (excellent) extensions,
plus
McAfee SiteAdvisor - displays web-site safety rating based on automatic analysis and user reviews
BugmeNot - bypass compulsory web-site registration
Opera style All-in-One Sidebar
CustomizeGoogle - remove ads, add links to web archive, other search engines, anonymize cookies, make image search link to image directly, remove sponsored links
Google BrowserSync - synchronize bookmarks, cookies, and, optionally, history in different browser installations - at home, at work, etc. Not recommended for are privacy-paranoid
All extensions are compatible with Firefox 2.0