Hi GoBlue,

Ajuga can take wet, but not boggy, soil, and Sweet Woodruff, Galium odoratum, can take boggy conditions. But be careful with the sweet woodruff, it can spread a lot, even with just normal moisture. Both can take sun or shade. I just thought of another one. Myosotis scorpioides (a/k/a M. palustris), Water Forget-me-not. It can be grown as a water plant, so it can definitely take boggy conditions. Here's a link with more info about it.

Skybird

Here is a link that might be useful: Water Forget-Me-Not

Look into the Dryopteris family of ferns- some of them- Christmas and Autumn, are evergreen. Though they may not be evergreen for you. Some ferns will take a bit of sun if kept moist, also.

Ferns and ponds seem like a natural to me.

Is Mazus reptans hardy up there? That will take the damp as well.

Also check out some of the irises- Siberian comes to mind, some of them will take a lot of water.