IDM like Download Manager for Ubuntu (wxDownlad Fast)

There are plenty of them! Just have a look in Synaptic.
Freeloader, d4x, jigdo, kget, gwget, aso.

If you are running firefox you can try a really nice download manager that is also an add-on called DownThemAll. It can be found at:
https://addons.mozilla.org/en-US/firefox/addon/201

Apparently, my prayers got answered when I found a program (wxDownloadFast) that uses multi-threading:
http://dfast.sourceforge.net/
Download the hardy heron version safely from here
http://www.getdeb.net/app.php?name=wxdownload%20fast

Also the getdeb.net site has a copy (FIESTY n GUSTY):
http://www.getdeb.net/app.php?name=wxdownload%20fast

I have downloaded the program and it seems it does what it says in the multi-threading department. And it is "fast". And apparently you can also specify extra web sources for the same file to increase the downloading speed.

I’ve read issues online with the fiesty package, but the edgy package form their site seem to work fine.
link to package working for me in gutsy
http://prdownloads.sourceforge.net/dfast/wxdfast_0.6.0-1_ubuntu_i386.deb?download


To be able to use wxDownloadFast as the default download manager and integrate wxDownloadFast into firefox u need to install flashgot for firefox, this can be done through firefox add-ons.
- Restart firefox, and then go to Tools -> Flashgot -> More options. Here click on GENERAL tab and then select wxDownloadFast as your download manager.
- Then go to DOWNLOADS tab and check “auto start downloads”, also check “intercept all downloads”. Ok your changes and check to see if all your downloads form firefox are sent to wxDownloadFast