Can I use my Digital Camera or MobilePhone Camera as a web Camera to chat through yahoo?

Yes you can !!!!

U hv to download a software for that in your phone..
and yes gprs must be enabled surely...

i dont know about your phone but you can use your camera. my friend uses her d-g cam but i cant use mine so i guess it depends on the cam

Yes!

I don't know about digicams, but you can sure use your mobile phone's camera for the purpose! But you need to activate GPRS for that. There are many applications available on the net for this.

Just search for Mobile Webcam on the net. You might get other options which do not use GPRS. (Bluetooth probably?)