Aberdeen, not cliff jumping per se but there are a bunch of boulders and deep pools the stream flows around/through just upstream from the bridge on mill. we used to park right along the road there but anymore there are no parking and private property signs because some kid got hurt and his parents tried to sue the property owner. the dude is cool though and as long as you arent there at night time, dont leave any trash and take down any dams you build hes not going to care, or notice. park elsewhere and hike down from the conewago trail to get there.
If you are hardcore go find a deep quarry. If you are softcore theres always gretna