I am not from PNW, so these may not apply. Most are for foliage, as wow-popping flowers usually need sun.

heurchera (foliage comes in many colors)
astilbe
solomon's seal
lily-of-the-valley
cardinal flower (red blossoms)
hostas
azaleas
hellebore
coleus (lots of different foliage color choices)
impatiens (for flowers)
bleeding heart
wood poppy
foxglove (native varieties are smaller and yellow)
iris reticulata and lots of bulbs for spring

in other words, there are lots of choices. Ask someone knowledgeable about your area and enjoy!