Creeping thyme starts easily from seed and spreads fairly rapidly close to ground.You can also snip a bit to use in cooking as you need it.

Ive seen a lot of people in our area plant blue rug juniper on steep slopes. Also you could try daylilies, they do well holding up soil on hills. Not sure if these are considered groundcovers, but you could give them a try.

On my hill I use Daylily (Hemerocallis fulva)and Nepta"Six Hills Giant" together. I like this daylily because it spreads by runners where as the hybrid daylilies are clump forming. Both the daylily and the nepta put on a great show.