I collect these addons and use them everyday ，all of them are wonderful and useful，but i am not sure they are also stable，sometimes i found i got missing using them,so be careful to try it
Are you concerned about your privacy? Or, are you blocked from some websites by a firewall? And, are you arming yourself with a proxy? In that case, AutoProxy is designed for you! A tool to help you use your proxy automatically & efficiently.
Allows bidirectional access to Google Calendar
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.
Google and Zimbra contact sync for Thunderbird. (TB 24 and above NOT supported)
Displays the address books in a sidebar in Thunderbirds 3-pane-window and can be toggled with the F4 key or a toolbar button.
Visit my Contacts Sidebar site for recent versions and news.
Quickly get to the latest nightly build of Lightning relevant to the version of Thunderbird and the OS you're on.
Collections are groups of related add-ons that anyone can create and share.Explore Collections