For your Chrome/Chromium web browsers... it has a separate extension but by default it integrates with Firefox4/3.6+ nonetheless. Here are few of its main features that you'll get with this latest release.
*. Since we all know that Unity and many other major desktops are "obsessed" (not a judgment :) ) with application indicators, Steadyflow 0.1.7 now includes a better indicator menu through which we can control the downloading files with ease (pause/resume/pause-all, etc)
*. Newly added "copy URL", for adding a URL/download link easily.
*. Now it has an icon of its own for the Unity's application launcher (drag-n-drop files for star downloading).
*. Start/Pause or Delete multiple file downloading at once.
|New "indicator menu"...|
*. Added support for password authentications for HTTP, HTTPS, FTP, and SMB, etc... are among the main features according to the developer.
You can install Steadyflow 0.1.7 in Ubuntu 11.04 Natty Narwhal by using the below command in your Terminal window.
sudo add-apt-repository ppa:sikon/steadyflow
sudo apt-get update
sudo apt-get install steadyflow