Hello Jeremy,

To some degree what you decide to plant will be determined by the budget you are most comfortable with. Planting low growing shrubs, like low grow sumac would be one good option, but then shrubs, even small ones, would be the most costly route.  

Scattering seed would be the most economical and you could use something like Dutch White Clover.  This would give you a mass of low growing, maintenance free ground cover rather quickly.

Planting ground cover that you purchase as cell plugs is another route and  is a middle of the road approach.  I love ground covers like myrtle or ajuga, which blooms blue in the spring, or sweet woodruff which blooms white in early summer and covers a shady area really quickly. 

Another idea is Liriope miscari - it has wider low stripy leaves and this also comes in cell flats - basically, a flat of small plugs that you pop in the ground. Liriope is very tough and easy to ignore, although it does spread so make sure it is not going to go into areas where you do not want it. 

Once plants are established they should do well, but it takes a few years to fill in for most any of these.  You could scatter some bales of pine straw while the plants are getting started to minimize weeds and trap moisture and stabilize the hill soil a bit. I would not plant in the heat of the summer or during really dry spells, in order to give your effort the best chance at survival. 

Hope this helps,

Kathleen