FireFox Extensions that I use:

• 1-Click Weather
• AdBlock Plus
• Answers.com
• Better Gmail 2
• BugMeNot
• Bookmarks Synchronizer
• del.icio.us Bookmarks
• fasterfox
• Firebug
• YSlow (Firebug addon)
• GMail Space
• GMail Skins
• Google Browser Sync
• Google Toolbar
• Gmail Manager
• Greasemonkey
• ExpertsExchangeFilter
• GMail Agenda
• GMail Full Width 2 (no longer works)
• GMail Spam-count Hide (temp fix)
• Google Filter (Remove certain sites from results)
• Greasemonkey: Google Account Multi-Login
• Remove all Facebook Ads
• ScrabuCheck
• Live HTTP Headers
• PackageMapping.com Extension
• Remember the Milk GMail Integration
• ShowIP
• SnapBack
• Tab Mix Plus
• Tab Mix Plus Dev Build
• Torbutton
• Update Notifier
• Web Developer
  
  
• Copy URL+
• IE View
• FlashGot (use w/ext. download manager)
• Foxylicious
• foXpose
• ListZilla
• PasswordMaker
• PDF Download
• SwitchProxy Tool
• SecurePassword Generator
  
  

Thunderbird Extensions that I use:

• Lightning Calendar Integration
• Google Provider caldev Sync (bi-directional!) lightning or sunbird with google calendar
• lifehacker article on syncing desktop calendar apps with gcal
• Contacts Sidebar
• Enigmail
• MinimizeToTray
• Quote Colors
• Sender Verification Extension
• Update Notifier
• View Headers Toggle Button

Plug-Ins for OSX Firefox

Settings:

From http://www.mepis.org/node/5420

FireFox-Tweaks
(type in address bar about:config)

browser.blink_allowed", false
browser.cache.disk.capacity", 65536
browser.cache.disk_cache_ssl", true
browser.cache.memory.capacity", 65536
browser.display.show_image_placeholders", false
browser.sessionhistory.max_entries", 10
browser.sessionhistory.max_viewers", 5
browser.tabs.showSingleWindowModePrefs", true
content.interrupt.parsing", true
content.max.tokenizing.time", 1
content.maxtextrun", 4095
content.notify.backoffcount", 1
content.notify.interval", 1
content.notify.ontimer", true
content.switch.threshold", 1
dom.disable_window_flip", true
dom.disable_window_move_resize", true
dom.disable_window_open_feature.close", true
general.useragent.override", "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.9)
image.animation_mode", "once"
network.ftp.idleConnectionTimeout", 60
network.http.keep-alive.timeout", 30
network.http.max-connections", 48
network.http.max-connections-per-server", 24
network.http.max-persistent-connections-per-proxy", 16
network.http.max-persistent-connections-per-server", 16
network.http.pipelining", true
network.http.pipelining.maxrequests", 10
network.http.proxy.pipelining", true
network.http.request.max-start-delay", 5
network.prefetch-next", false
nglayout.initialpaint.delay", 0
plugin.expose_full_path", true
ui.submenuDelay", 0