Echinacea.

Our Asiatic lilies and delphiniums are providing a lot of color right now. Daylilies are also starting to put on a show. All of them will grow in part-shade.

Ligularia, Thalictrum, & Actaea.

In addition to the suggestions aboveÂnote that actaea is a reclassification of cimicifuga, snakeroot, which is a terrific perennial I'd add astilbe and Celandine poppy (stylophorum diphyllum, much under-used in my opinion; it's a trouper), also, and despite opinions to the contrary, lots of different clematis, which you can grow nicely on a pillar or tripod kind of thingie in partial (even fairly heavy) shade. Gary

Also, penstemon, monarda, heuchera, clethra, and early-blooming hosta.

Thanks, everybody! I can't wait to check these out.

garystpaul, I wonder if your woodland poppy is actually lesser celandine - they have smaller flowers and brassica seedpods. I saw them blooming at yesterday garden tour while woodland poppy should have been mostly done now.

I will add:
Hydrangea
Fern Leaf bleeding Heart (depend on what species or variety)
Goatbeard - American, Korean (almost done) or hybrid of the two.
Queen of the Meadow