The official website of NDTV Imagine television channel is now providing an opportunity to download the title theme song of Ramayan that is now being telecast. Apart from the title theme, you can also download wallpapers, a doha, songs like Sita Jay Mala.
Pictures of Ram, Sita and the main episodes of the Ramayana serial can also be downloaded.
Wallpapers, songs and pictures can be downloaded from this link. (link removed)
Update: It seems the songs have been removed from the official website and is now available in CDs and DVDs. It is copyrighted and not available for free download.