XKit: The extension with 70+ extensions for Tumblr.
XKit is a browser extension that allows you to do more than you thought possible: from saving your sent ask / fan mail to it’s outbox to viewing what tags people added to your posts at a glance, completely blocking posts you don’t like, automatically blocking posts from people by type, theming your dashboard, checking your post limit, finding inactive blogs you follow, bulk replacing tags and much more. And new extensions are added to it’s extension gallery nearly every week.
It’s available for Chrome, Firefox, Safari and Opera.
For the full list of extensions available for it, click here.