Firefox extension Google Calendar Notifier alerts you of your Google Calendar events in your Firefox browser, polling Gcal every minute for a new event.
In order to use the Gcal Notifier, you need to have a shared calendar or use a private feed URL, then add it to the extension’s options.
Google Calendar Notifier
Rate [...]

The Google Calendar Quick Add Firefox extension enables a keyboard shortcut in Firefox that adds events to Google Calendar without having to visit the calendar.
Once the extension is installed, hit Control+; (semi-colon) to get a prompt as pictured. Quick add your event and in it goes to your Google Calendar. Keep in mind you [...]

This is a Firefox extension that allows you to manage multiple gmail accounts and receive new mail notifications. Displays account details including unread messages, saved drafts, spam messages, labels with new mail, space used, and new mail snippets. Features

Manage multiple Gmail accounts
Receive new mail notifications
Tooltip with account details including new mail snippets
One-click access [...]