Set up an empty game object in front of the door, make the collider a trigger, and attach an OnTriggerEnter code on it. Compare the tag of the collider and if it's "Player" tag, have the animation play and the door open.

HI....although a newbie to both Unity and scripting...i found this using Raycast, just make sure your door has a collider and Is Trigger is off....

var RayCastlenght = 2; //allows you to change the distance required to trigger the door

function update() { var hit : RaycastHit;

    //check if we are colliding
    if(Physics.Raycast(transform.position, transform.forward, hit, RayCastlenght))
    {
        //...check colliding with door
        if(hit.collider.gameObject.tag == "BookCase")
        {

            //move the case
            hit.collider.gameObject.animation.Play("BookCase_anim");
        }
    }
}

what you need to do is compose an animation for the door to open and then change Bookcase_anim with your new animation.....

best of luck