I just installed a pair of footwell lights in the Camry. Just run 2 wires to the dome light (need both the power and ground from up there) inside the headliner. Drop it down the pillar, across the floor under the door panel, then behind the footwell trim.
From there, I just found a place on each side to install a light that cost $2 at AutoZone.
I'm trying to figure out how to do the same in the 4Runner -- the sunroof looks like it will get in the way.