Extensions, plug-ins, add-ons, whatever you want to call 'em, Firefox 3 has 'em. In fact, though it may seem that many of your favorites haven't yet updated, you might be in luck. By visiting the home pages of several of the plug-ins I use, I found that most of them had either a functional, stable beta or a full update ready to use with Firefox 3. This collection of add-ons I use both at home and in the office, and can be used for the Windows, Mac, and Windows Portable versions of the browser.
You wouldn't think that AdBlock Plus is an essential plug-in, but once installed it changes the way you look at the Web--literally. By block advertisements from appearing, you can approach a somewhat more zen-like, 1996-looking Internet experience. Well, not really, but there's definitely a lot less clutter staring back at you.
Session Manager and Tab Mix Plus are must-haves for tab and browsing session management. Tab Mix Plus gives you what feels like an infinite amount of control over tab behavior, from how they open to how they close. It's a little overwhelming how much you can do with this add-on, so I recommend checking out the Download.com Tab Mix Plus user's guide.
Session Manager does for sessions what Tab Mix Plus does for tabs. Although TMP does save sessions, I found that to be the one feature that was lacking: during browser crashes, it often lost my tab sessions. Session Manager sorts out that problem fast, and allows you to keep and recall multiple tab and browsing sessions at will--among its other excellent features.
When Firefox is your main browser, there's rarely a just cause for the casual user to open up Internet Explorer. For the rest of us, IE Tab eliminates all the other reasons by forcing Firefox to render a page using the Internet Explorer engine. You must have IE installed on your machine for this plug-in to work, but the convenience and saved resources can't be beat.
FoxyTunes remains a top-notch plug-in and gets points for being one of the few to introduce new features with its update. FoxyTunes 3.0 adds the ability to turn any page into a playlist, as long as the Web page has music already embedded in it. For those who are new to this plug-in, though, it does much more. It lets you control your media player from the Firefox toolbar, and supports more than two dozen players including iTunes, WinAmp, MediaMonkey, Pandora, Last.fm, and more.
Fast approaching seven free gigabytes of online storage, you can turn your Gmail account into something more than a mere e-mail client with Gmail Space. The FTP-style split-screen interface is instantly recognizable, and it sends you an e-mail notification when you upload a file. Create a simple filter and a label and you never have to worry about transferring files again--as long as Google's servers remain impregnable, at any rate.
FaviconizeTab and Tab Scope are the perfect one-two punch for a tab addict such as myself. FaviconizeTab utilizes a hotkey command to turn any tab into the size of a favicon. This won't stop you--or me--from having 20 or even 40 tabs open, but it makes them take up a lot less space. Tab Scope provides Opera-style mouse-over previews of your tabs. So, if you can't remember what your faviconized tabs were, perhaps a quick preview snapshot will jog your memory.
Like AdBlock Plus, you don't know you need DragDropUpload until you install it. The add-on gives you the ability to drag a file from your desktop into any text field in a Web page. Lightweight but extremely effective, if you e-mail a lot of attachments, this should quickly become a massive time-saver.
Download Statusbar is a tool I use at work for discovering the absolute URL for files that I'm downloading. It can be used for much more, though. It opens a second status bar when you begin downloading a file, and lets you manage the download via context menu options. I'm not a huge fan of having to open many of Firefox's secondary features in new windows, and I find this to be much more convenient.
AIOS, or the All-In-One-Sidebar, allows me to force the Add-ons and Downloads windows in a sidebar, but it also creates a collapsing sidebar that comes with a secondary toolbar. I have it set open my bookmarks, history, and page info as well as add-on and download lists, but I also use the toolbar to hold links to FireFTP, Gmail Space, my Del.icio.us bookmarks, and a "Restart Firefox" button provided by MR Tech Toolkit (formerly known as Local Install).
Do you have a favorite Firefox extension that has--or hasn't--been updated for Firefox 3? Tell me about it in the comments below.