Firefox Extensions

Functionality:

1. Xmarks
   Sync or backup bookmarks and passwords
2. FEBE
   Backup your Firefox profile and extensions
   

Appearance:

1. AdblockPlus
2. Download Statusbar
   Downloads show up in the status bar, Chrome-style
   
3. Fission
   Combine the progress meter with the address bar, Safari-style
4. Locationbar2
   Formats and linkifies addresses in the location bar. Makes the domain stand out, IE-style.
5. Omnibar
   Integrates search bar to the location bar, Chrome-style.
   
6. Link Target Display
   Install this and you can turn off the status bar, Chrome-style.
7. Tab Progress Bar
   Provides a progress meter for each tab
8. Tab Scope
   Popup previews for tabs
   
9. Google Toolbar for Firefox
   
10. Menu Icons Plus
    Adds icons to menus. Really improves the appearance of Firefox. These should be included with Firefox.
    
11. ImageZoom
    Right-click to enlarge any image. Now you can hold right-click and use the wheel to zoom.
12. TinEye Reverse Image Search
    Right-click on an image to find other instances of that image. Useful to find out if the image was photoshopped, or for larger versions.
    
13. RestartFirefox
    Should be built-into Firefox. Adds a "Restart" menu option to the file menu.
14. Menu Editor
    I use this to remove the "Open in New Window" menu entries.
    
15. LineMarker
    Occasionally it's useful to be able to mark a line on a web page; e.g. when reconciling a bank statement, to be able to mark the transactions you've already gone through.
16. BetterGmail2
    I prefer the IMAP interface to the web one, but this extension does add some cool things to the Gmail experience: hover color change, and Target Alert-style icons for attachments in the inbox view.
17. Duplicate Tab
    Comes in handy every once in a while
    
18. Linkification
    Also comes in handy every once in a while