Updated 8/23/07 -- new comments in italics

So I promised a list of all the firefox and thunderbird extensions I'm currently using. First, a few of the extensions I no longer use or didn't get a chance to cover here are covered in an older blog entry [1] of mine, so feel free to check that out. Also, folks need to make sure they're using imap [2] for mail. If you're not, well, there's no gentler way to say this than you're lame. IMAP r0x0rs your b0x0rs.

Anyway, please feel free to add comments with your suggested extensions.

Firefox

Usability Tweaks

• Greasemonkey [3] - Meant to allow javascript files to modify certain websites every time the browser renders them. Sounds boring, but it's not -- greasemonkey scripts can "fix" broken website behavior, or add nifty new features userscripts.org [4] contains the biggest repository of scripts. -- I rarely use any greasemonkey scripts these days
• Adblock Plus [5] (with Filterset.G [6]) - Most ads on the web are obnoxious. Use these two extensions to make them go away. -- Still indispensable
• Locate in Bookmarks [7] - If you have a lot of bookmarks in a lot of folders, the bookmark search function can be a real hassle to work with it. It doesn't show you where a found bookmark is contained so you can't navigate to that folder and find the other nearby bookmarks. This simple extension adds a right-click option to "Locate" a bookmark. -- Still indispensable
• BugMeNot [8] - bugmenot allows you to login to free sites that require logins by taking advantage of a community developed list of bogus accounts. No more making up fake info every time you want to read a NYTimes story anymore... -- Still indispensable
• Flashblock [9] - this simple extension replaces all flash elements with a clickable box. If you want to see the flash, click it. If not, ignore it and be glad that you didn't have to worry about that damnable punchable monkey.-- Superseded! See NoScript below
• Search Keys [10] - Great little extension by Jesse Ruderman (who also is the author of a number of my favorite bookmarklets [11]) and my most recent extension install. Adds a way to quickly navigate search results using the keyboard. -- Still great!

Make it purdy

• Reveal [12] - True eyecandy. Just install it. You won't regret it. Surprisingly, it's actually pretty functional too. -- Sadly, no longer works in FF 2.0
• Forecastfox [13] - Your mom wants this extension. Or rather, she doesn't know it, but she needs you to uninstall weatherbug and install this extension. Simple, customizable, and useful weather monitoring extension. -- Yup, still using it!
• Tab Mix Plus [14] - Easily in the top 5 of my favorite extensions, tab mix plus has tons of amazing features. My favorites are the session saver ability (I used to have a separate extension just for that, but TMP does it better anyway), being able to see tabs loading status in the background, and customizing exactly which icons appear on my tab toolbar. And if you're a true tab fiend, you'll love the ability to have multiple rows of tabs. -- FF2.0 has some of the few features I used to use TabMixPlus for, but it's still highly recommended

Web development/hacking

• New item! -- NoScript [15] - best browser extension ever for security. Can be a usability hassle and might not be recommended for all users, but it's the single best protection you can add to your browser to ensure you're secure against the latest exploits.
• New item! -- Safe History [16] - Along with Safe Cache [17], two great extensiosn that enhance security by keeping websites from being able to detect what websites you've visited. Very little impact on user experience for a big security boost.
• New item! -- Slogger [18] - Not quite conveniant for any of these categories, Slogger is nonetheless essential. In short, it will automatically archive and cache every webpage you visit. While this doesn't sound all that useful initially, it's quite flexible for logging in various format, and can be incredibly useful for quickly browsing content from your history while offline, or even cooler, to create a local search index of all web content you've viewed over a period of time. Use a desktop search tool like beagle or tracker to automatically have quick searches over your web history. This is incredibly useful.
• Aardvark [19] - Allows you to visually edit the page DOM on the fly -- remove elements, see different properties, etc. Use in combination with Platypus [20] and GreaseMonkey to make changes permanant every time you visit a page. -- Not commonly used, but nice to have.
• Web Developer [21] - This extension is indespensible. It does so many useful things whether you're a web developer or not that I'm not even going to get into it. You can spend days just playing with all the features. -- Just as useful as ever
• Live HTTP Headers [22] - Manually edit request headers and see the current server response headers in the page info tab. The server response headers are visible from Web Developer, and I prefer Tamper Data for data munging, but some folks like live http headers. -- Always handy
• Tamper Data [23] - If you hack websites, you need this plugin. Basically a simple in-browser version of some of the more fully featured proxy products meant to be used to tinker with web apps, like WebScarab [24], and Paros [25]. -- Essential webhacking tool
• Firebug [26] - Slick javascript debugger useful for web developers and web hackers alike. -- Don't use it quite as nearly as much as I probably should
• Switchproxy [27] - Quickly switch between proxy setups. Useful for anonymous browsing, or just turning testing on and off using Paros or Webscarab as mentioned above.
• User Agent Switcher [Array] - There are other ways of changing the user-agent string, but this extension is the simplest most conveniant.

Thunderbird

Pine-ification

I used pine and mutt for a long time. So long that I had to hack thunderbird to make it more CLI-like. The following extensions helped out tremendously:

• TB QuickMove Extension [28] - All of these first three extensions focus on being able to move messages into different folders with the keyboard. QuickMove is the simplest -- map different folders to CTL-0 through CTL-9 keys and quickly move the selected message when you hit the key.
• Quick File [29] - Quick file adds a much more versatile interface to allow you to save messages by typing out a folder name. It will automatically match the appropriate folder for you and let you tab-complete. My favorite features are the ability to set a default save location and the preference to only search folder names of folders on the same server as your current folder.
• Nostalgy [30] - If I only had one thunderbird extension, nostalgy would be it. It's similar to Quick File in that you can save by folder name, but it has a better interface and allows you to navigate to folders using the same method too! The only drawback is that it doesn't have a preference to limit folder searches to the current account, so it sometimes requires a few more button pushes than I'd like.
• keyconfig [31] - Can't have a pine-like experience with Thunderbird keybindings. So fix them with the same extension you use in Firefox to tweak its keys.
• Virtual Identity [32]

- This isn't pine-like, but mutt had an awesome concept of "alternates". I could tell mutt what all my email addresses looked like and when someone sent a message "to" a different address (since I have all email @psifertex.com forwarded to the same address), mutt would automatically change my reply as appropriate. Well, I can finally do the same thing in thunderbird thanks to virtual identity. Still have some complaints about the way it operates, but it's much closer to the behavior I missed so much in mutt.

General Tweaks

• Sync On Arrival [33] - By default, Thunderbird doesn't actually download message bodies of messages until you select them or you go offline -- even if the folder storage is set to save all messages. This tweak aims to change that behavior so that when mutt gets new headers, it automatically gets bodies too. Useful if you go online/offline a lot and hate waiting for the offline download to complete.
• Feel like thunderbird is missing some buttons? Well, add 'em.
• Mnenhy [34] - I mainly use Mnenhy for the custom header options, but it's got a ton of other features as well. The equivalent of web developer for thunderbird in that you can tweak and customize lots of different otherwise hidden settings.
• FolderFlags [35] - So what if you have folder names than are different than the default ones that Thunderbird makes. Say your spam folder is named "spam" and not "Junk". This excellent extension allows you to set the internal flags for all your folders.