Recently i have had a whining noise coming from my alternator on my 2002 3.4L , you can feel the vibration if you place your hand on it! as you accelerate , the whining gets louder! I have no issues with my battery (knock on wood) just the whining noise. Any ideas?

bearings on the pulley?

 

Pulley bearings probably.

Are you sure it's coming from the alt and not the water pump or belt tensioner?

 

Are you hearing the whining under the hood or through the stereo?

 

With the Alt right on top, i tried to put my ear as close as possible, and put my hand on the Alt there was vibration.

What is the best way to test which one it is? i should probably take the belt off, i think its the original one. Should i turn the 3 pulleys you mentioned by hand?

 

No, not through the radio, under the hood.

 

You can use a long screwdriver and carefully put it on the water pump, alternator, and belt tensioner while the car is running, and listen (like a stethoscope). The one that is loudest is most likely the one with failing bearings. Be very careful that you don't touch the serpentine belt while doing this, though.
If you release the belt tension and spin the pulleys by hand you might be able to tell that way. I think I would try that first since it is so easy.