Andro Tones which is available freely on android market, anables you to use muliple ringtones for each contact. This will switch between the allocated ringtones for each contact when recieving a call from a particular contact. Check this out guys. Really Awesome app. Make sure to leave a comment on the market.

This is the link to the App - https://market.android.com/details?i...MuYW5kcm9pZCJd