Based on Neil Blevins' object planter. This script allows you to select two sets of objects and plant / parent them to another set of geometry that is "below" it. Ideal use: you have a bunch of props and need to plant/parent them onto multiple ground pieces... you can select all the trees, select all the ground pieces, and it'll automatically parent to the object below it.
Notes:
*Sometimes it will parent to wrong objects... i find that a reset xform on the parent objects help.