Someone asked what addons I'd downloaded into my Firefox browser, so here's the full list:
• abcTajpu
    a` b\ c^ ---> à β ĉ (lingvo.org/abctajpu)
• Answers
    Alt+Click on any word or term for quick info (definitions, up-to-the-minute reference, and more). No selection is necessary!
• Copy Link Name
    Copies the name (source) of a link.
• DOM Inspector
    Inspects the structure and properties of a window and its contents.
• Download Embedded
    Downloads all embedded objects on a webpage.
• Download Statusbar
    View and manage downloads from a tidy statusbar
• DT Whois
    Domaintools.com whois button for Firefox
• Exif Viewer
    Extracts and displays the Exchangeable Image File (Exif) data, as stored by digital still cameras, in both local and remote JPEG images.
• Fasterfox
    Performance and network tweaks for Firefox.
• Firefox (default)
    The default theme
• Flashblock
    Replaces Flash objects with a button you can click to view them.
• Forecastfox Enhanced
    Get international weather forecasts and radar images and display it in any toolbar or statusbar with this highly customizable extension.
• Foxmarks Bookmark Synchronizer
    Synchronizes your bookmarks across machines.
• FoxyTunes
    Control any media player from Firefox and more...
• Html Validator
    Adds HTML validation to the View Page Source of the browser. The validation is done by Tidy from W3c.
• Image Zoom
    Adds zoom functionality for images
• MeasureIt
    Draw out a ruler to get the pixel width and height of any elements on a webpage.
• Nuke Anything Enhanced
    Allow hiding of almost anything via context menu
• Parent Folder
    Go up a folder level
• Print/Print Preview
    Replace the default "Print" button with the Mozilla Suite style "Print/Print Preview" toolbar button/menu. Adds new options to context menu as well.
• QuickRestart
    Adds a "Restart Firefox" item to the Tools menu.
• Searchbar Autosizer
    Auto resizes the searchbox as you type
• Search Images With a Single Click
    Highlight search criteria with the mouse, right click, and choose "Search Images"
• SearchWords
    Add keywords to your search engine
• Server Spy
    Indicates what brand of HTTP server runs on the visited site.
• SmoothWheel
    Scrolls the document smoothly when scrolling the mouse wheel
• Split Browser
    Splits browser window as you like.
• Stop-or-Reload Button
    Turns the stop and reload buttons into a single one. When you can stop, you have a Stop button, otherwise you have a Reload button. (Like Safari)
• Sun Cult
    Worldwide Sunrise, Sunset, Twilight, Moonrise and Moonset Times
• Tab Catalog
    Shows thumbnail-style catalog of tabs.
• Tab Mix Plus
    Tab browsing with an added boost.
• Talkback
    Sends information about program crashes to Mozilla.
• Tiny Menu
    Replace the standard menu bar with a tiny menu popup.
• User Agent Switcher
    Adds a menu and a toolbar button to switch the user agent of the browser.
• VideoDownloader
    Download videos from Youtube, Google, Metacafe, iFilm, Dailymotion... and other 60+ video sites ! And all embedded objects on a webpage (movies, mp3s, flash, quicktime, etc).
• Web Developer
    Adds a menu and a toolbar with various web developer tools.

for screenshots, or to install it for yourself, go to the addons page addons.mozilla.org/firefox/extensions and enter the name of the extension (as seen above).
One thing to do is not to restart your browser after each install of an addon, just download a number of the above or other ones you find, then restart (which is just a click in the addon box) to enable all of them at once.