Mouse position script...

Hello. I found this script on the Unity wiki. It allows objects to be dragged around the screen using the mouse. How would I go about modifying it to do the following things?

1:Have the object always follow the mouse, rather than working only when the mouse it being held down.

2: Currently, it only works along the X/Z plane (that is, the camera is looking down from the y axis at the object), how can I make it work along the X/Y plane?

Thanks.