These pictures are from a few days ago, but this is pretty much all I've been doing lately. We're building the retaining wall 'above' the house spot out of old broken concrete ("urbanite" for those in the natural building world) with rebar and mason's mortar. It's actually quite pleasant to do, especially if you can keep out of the sun.
I got the rebar from my neighbor, who has a gigantic pile of the stuff. This is going to be a pretty strong wall. I'm also tying the rebar within the wall to the roots of the tree stump that's above the wall.