How about mulching the area with leaves? If you do a quick search for erosion and organic matter/ mulch you will find some interesting articles.
Water hits the leaves and soaks in, then the surface erosion is decreased.

Michele,
You spell your name the same way my daughter and sister do. Don't see that too often. :)
Have you considered vinca minor as a ground cover? There is plenty of it growing under the old oaks near my garden. The leaves are a nice, dark green and the blue flowers are pretty. It seems to thrive no matter what the conditions and spreads easily. Oh, and the area is quite hilly. If you would like some, let me know via email.
rosebush

Since drought seems to be a problem you might want to try drought tolerant plants. I like native prairie grasses. For a little bit of shade tolerance I have used creeping red fescue.

I have a large maple on a slope. I followed the advice of a local master gardener... I put down ten bags of 'soil conditioner', stapled burlap to the entire area, then put down ten bags of mulch. I shred leaves each fall and put it on top of the mulch. I continue to try the occasional plant, but everything struggles. The master gardener said I might have to redo the soil/burlap/mulch every 3 or so years.

Maples make dense shade, have some roots close to the surface and can be greedy. That said, there are probably some plants that adapt well to maples so maybe you can find out what they are and plant them.