The default download manager in Firefox isn't exactly great. Download Statusbar puts it on steroids and gives Firefox a truly excellent download manager.
Download Statusbar is a Firefox add-on that remains discreet until you need it. There is nothing to configure before using Download Statusbar. As soon as you download a file a download indicator appears at the bottom of your screen.
From here you can stop and start downloads as well as copy the source URL of the download. Specific information is given about the file size, how long remaining on the download and average download speed. If you open the configuration options, there are some options you can change relating to how Download Statusbar manages download and how visible it is.
Download Statusbar is very convenient and adds many much needed features to Firefox's own downloader.