Fireshot

FireShot is an add-on to the Mozilla Firefox browser that allows you to create screenshots of the pages you open. Unlike other tools of this kind, this add-on provides the user with a number of tools for editing a screenshot and adding graphic and text annotations. Such functionality will be useful for web developers, testers and editors.
Screenshots can be uploaded to an image server, saved to disk (in PNG, GIF, JPEG, BMP formats), copied to the clipboard, sent via email or exported to an external editor for further processing.

View flash presentation (carefully, it starts by itself)

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Compatibility on 05/14/2008: * Firefox: 2.0 - 3.0pre

From myself I will add that after it caught my eye, I take full advantage of it. Convenient, understandable and usable. In the comments I saw the recommendations of this plugin, but did not notice the topics. See and use. Recommend :)