raycast help need

What your code does:

//Every frame
function Update  () {
    //Casts a ray 100 units in the direction x=-1, y=-1, z=-1 from the current position.
    //You are always casting in the same direction in world space, not relative to your
    //character.
    var hit : RaycastHit;
    if (Physics.Raycast (transform.position, -Vector3.one, hit, 100.0)) {
        //Unless your ground is always diagonally down in world space, this variable is
        //misnamed, especially since the diagonal distance is less consistent and
        //probably not what you wanted anyways.
        distanceToGround = hit.distance;
        //Since you aren't casting in front, this message is wrong.
        print ("There is something in front of the object!" + distanceToGround);
    }
}

What you probably want:

//Every frame
function Update  () {
    //Cast a ray 100 units in the forward direction from the current position
    var hit : RaycastHit;
    if (Physics.Raycast (transform.position, transform.forward, hit, 100.0))
        print ("There is something in front of the object!" + hit.distance);
}

You should really try to understand what your code is doing - it becomes very obvious what's wrong when you know exactly what's happening step by step.

In order for the raycast to work, the object you want to collide with will need to have a collider attached. Also, I recommend using layers and a layermask to reduce the cost of the raycast.