You could do almost any of the ferns: cinnamon, ostrich, hay scented or New York would all work. Better yet you may want to think about Christmas or autumn ferns, which do not go as dormant in the winter. Then you could add perennials for color contrast with silvery pulmonarias, mazus reptans, foam flower, lamiums, and/or even some of the brunneras although they may not bloom. Impatiens can be added annually for color or consider having a couple of pretty urns that you swap pots of flowering plants into throughout the summer.

You didn't say what city you are, but almost any real garden center will have any or all of those plants. If you are in D.C. (as your handle suggests), try Behnke's (especially the one in Beltsville, MD for shade plants), American Plant on River Rd, or Craven's in Arlington for the largest selection of shade plants.

Hostas are not really deep shade plants, but the problem may lie more with what they are planted in than with where they are planted. I would first look at the quality of your soil before I invested in a lot of new expensive planting.