It can do miracles. Say if you are feeling lonely, hear a song that you love. It will help you...
 

Binod's collections
Hindi Songs on Kareeoke
Coolgoose for songs in all languages This is the best site for downloading malayalam, tamil, hindi songs (or any language).You can create your own login account and can download upto 50 songs a day. Also if you have nice selections at home, you can upload it to this site and share it with the world !! The quality of the songs is great, the format is MP3.
Music India Online Recently I took M.S.Subhalakshmi's Shiva Panchakshari Sthothram for bharatnatyam performance from this site. Thanks to the people behind the "Music India Online" site.
Malayalavedhi
Few Songs are here

Vismayam -Another collection of malayalam film songs
Devotional Songs chategorised by Ayyapa, Shiva, Ganapathi, Hanuman, Krishna, Rama, Venkateshwara etc.
Vayalar Kavithakal
More devotional songs some of it can be used for Indian classical dances.
For Oppana/Mapila Paatukal
I selected the "Palanjum Punjiri" song for organising-choreographing-teaching (for free) oppana for SICA's Dance of India program. Thanks to Masood for the song !
For Chitra's Album of Mappila songs