Download Manager Tweak is a modest name for a fantastic Firefox extension. This "tweak" is actually a complete reworking of the Download Manager, i.e. the box that pops up to show you the progress of all of the files you're currently downloading. Apart from making the UI 100% more attractive, it also adds a customizable toolbar (with especially handy "Open folder" button) and, best of all, it allows you to choose whether you want the Download Manager to appear in its own window, in a new tab, or in the a sidebar.