It is not easy to determine from your post exactly how much shade you are working with but a good many shrubs will grow quite happily in partial shade including all those you mention (most hydrangeas are really 'shade' plants and Japanese holly can grow well in nearly full shade). A visit to a local garden center should broaden that selection significantly, based on what they stock for your area.

FWIW, your limiting factor may not be the slope or the shade but rather the proximity to the maples. Planting within the primary root zone (under the dripline) of an established maple is problematic at best. Start small and provide some TLC to get things established rapidly (starter fertilizer, terrace the plantng holes, plenty of water).

Plants that can tolerate considerable shade and are relatively drought tolerant when established include aucuba, English laurel, yews (Taxus species). These are all evergreen as well, providing a more ideal screening function. You could also look at the Japanese holly or boxwood, even evergreen euonymus, although these may be much slower growing and less effective at screening in th short term..

Norway maple is quite possibly the worst tree species for growing under. Norway maples are alleopathic, their roots extend well beyond the drip line, are incredibly aggressive and the tree's dense canopy sheds rain like an umbrella. Before investing any money in plantings, really consider having some of the maples removed. Expensive for surre, but definitely worth it in the long run.

Thanks for your responses!
I do know about the evil Norway maple but unfortunately most of them that affect my garden are my neighbors. I am also guessing they were planted to prevent erosion when they built on this sloped site.

Thanks for the tips!

As for now I have to keep up with dividing my flowers as they haven't been divided for many years it seems!