DownThemAll is a very valuable Mozilla Firefox extension that allows you to download what you want by allowing you to selectively download files you select on a webpage. You can download one file or multiple files simultaneously.

Flashblock lets you control whether you want to see flash animation or not. When you load a web page with flash advertising or buttons the Flashblock addon will display a round button with an f in it. If you want to view the flash click on the Flashblock button that appears in place of the flash object and you will see the flash ad.