Best ap for transferring itunes music to a new Laptop - Laptop hdd died

Are all your music purchased from Itunes?  You'll need to authorize the computer first and you'll have the option to download purchased apps / music.

If not, you can enable 'use as disk' in Itunes so that you can view your device as a harddrive and copy files manually from there.  You can refer below

http://www.ilounge.com/index.php/articles/comments/copying-music-from-ipod-to-computer/P1

Senuti is a pretty good 3rd party app as well in addition to the previous poster.
http://www.fadingred.com/senuti/download/

You can also use the copytrans software where you can copy all the data from your iphone/ipod to your new computer. http://www.copytrans.net/copytransmanager.php

Once you copy everything, add the same to the itunes on the new computer and sync. No data loss should occur.

Thanks