Lost some of my purchases how can I get them back?

Hi I have lost some of my purchasesd when I had to format my hard drives and lost most of my music. I hadn't backed up my itunes library, which I will do as a matter of course from now one, but is there a way I can download some of the itunes I have previously purchased again without having to pay for them again?
thanks in advance


If you are in the U.S., then use the cloud:
Otherwise, you can transfer them from an ipod:  File>Transfer Purchases
Backup is very important.