Menu Wizard - Customize menus : Helps removing, moving and renaming menus and menu items
Chrome Download Manager - Chrome Download Manager. Bring Google Chrome like Download shelf into Firefox.
Download Manager (S3) - View and manage downloads from a tidy statusbar.
Status-4-Evar - That status bar was removed in Firefox 4.0.
JDownloader - JDownloader is a free downloading tool that enables you to download files from over a hundred hosting sites. The tool is compatible with Linux, Mac and Windows operating systems. Read more about JDownloader.
Extended Statusbar - A much more detailed overview of your browser activity