Tumblr Post is an add-on for Firefox that allows you to quickly post to your Tumblr account.
Sitting in the status bar, Tumblr Post's icon won't bother you unless you want to use it. Right clicking it will open a context menu where you can open your Tumblr dashboard, tumblelog or post directly. In settings you can add multiple Tumblr accounts if you want, and configure how Tumblr Post will work with different types of posts (image, audio and video etc).
This functionality would be enough to make Tumblr Post a great little add-on, but there's more. You can drag images, selected text, links, audio files and more directly over the Tumblr Post icon, and they will be automatically added to your tumblelog. It's almost too easy! This makes using the rich media(images, audio and video) capabilities of Tumblr incredibly fast and feels really natural.
If you use Tumblr, Tumblr Post is an essential add-on for Firefox, as it is such a capable, well designed application. After a little playing around, you'll never look back.