Tumblr Notifier brings notifications for new Tumblr posts.
Some Important features are as following:
1. A comprehensive tumblr client right in your Firefox side-bar
2. Notify you every time something happens on tumblr within the people you follow
3. Get badge notification on every tumblr action
4. Low bandwidth usage by exploiting to RSS technology
5. Features a quick Tumblr update to your profile
6. The new post you compose is automatically posted to your feed