My first thought when reading your request was a sedum groundcover of some kind. Dragon's Blood is a darker green leaf with deep pink flowers and there's a lime green leaf with yellow flowers with a name like kolanchoe. Each spreads but is easy to contain.

Also consider daylilies, they're pretty forgiving of sun and poor soil. So is periwinkle.

In my experience, pachysandra doesn't tolerate sun well and burns like bacon.

I agree, Sedum of some kind would be your best bet. There are many many types available, whatever your preference may be. You could also try creeping thyme. Good luck!

Jen

Sedum Angelina. It will grow into a nice mound in one season. Turns burnt orange in the winter.