Perennial Shade Garden Zone 4-5?

I'm fairly new to gardening and have a large corner of lawn that is shaded all the time. I've tried looking on websites but am having a hard time finding perennial plants that do well in full to partial shade. I do have 4 hostas and one rose bush, but the garden is a triangular shape that is probably about 20 square feet.....so those 5 plants don't cover much area! Any ideas or good websites are much appreciated! Thanks!!!