Download Managers are the must have applications for any O.S. to boost up download speed. Currently I am using latest version of Ubuntu 12.04. There are many GUI based download managers available for Ubuntu Linux. Currently I am loving these three download managers which works exactly to boost download speed.
Steadyflow is a GTK+ based download manager . It is easy to control and easy to use.
It is open source download manager in which many teams are involved for better result. It is also widely used in Ubuntu User.
Multiget is another download manager which I trust. It is very easy to easy. Just copy the url of the location the multiget grabs the location automatically.