Right. Avoid ajuga if you can. It moves into the grass and it very hard to eradicate. Many sedums work just as well in shade as sun, and are much more "refined". I also use phlox stolonifera, sweet woodruff and for small areas things like iris cristata. Sweet woodruff will spread, but can be easily pulled. If you have an area where you just want something green, and don't care about flowers, periwinkle works well. It also can be easily pulled out if it spreads more than you like.

You also might consider Pachysandra terminalis (Japanese spurge). There is a nice variegated variety that does well in shade.

Here is a link that might be useful: Variegated Japanese Spurge

Thanks...I read up on Sweet Woodruff, and it seems like it will not have an invasive habit on our hard clay soil, but is it evergreen? Everything I saw says it is deciduous.What does your phlox do in the winter.

Pachysandra is always a back-up, but it's just so overused. The variegated form is pretty, though.

Has anyone tried barren strawberry? (Waldsteinia ternata)

I have your same conditions and my DH is sick of pachysandra so I'm always looking for new evergreen groundcovers. I'm also using Wintercreeper (Euonomus(sp?). It has been very slow to cover and is vin-y like ivy. Easier to cut back than ivy, though. Try some interesting ivies. I found some unusual varieties in 6pks at Walmart a couple of years ago and they've done well, although I don't need full coverage with them...just spilling over boulders. My two new favorites, though, are perennials, Geranium macrorhyzum, which has small white flowers in late spring, turns slightly red during fall and is absolutely evergreen even in our last 3 cold, snowy winters and Campanula poscharskyana. It, too, is evergreen and has blue flowers most of the summer. Both like to have humus-y soil, so I dig in compost where I'm planting them.

I love partridge berry (mitchella repens).

Here is a link that might be useful: Patridge berry