Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
Organize your schedule and life's important events in a calendar that's fully integrated with your Thunderbird email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.
Google and Zimbra contact sync for Thunderbird. (TB 24 and above NOT supported)
Did your friend send you a cool link? Want to read the rest of that interesting article? Don't want to open up your web browser just to view it? You don't have to! Just view it in Thunderbird with ThunderBrowse!
abandoned, use Stylish Custom Add-on instead
custom additions to Stylish extension.
brings back features from 0.5.9 and adds new features