Oops, I knew I forgot to list one:
Philadelphus lewisii - Love the gorgeous midsummer blooms!

Common snowberry would probably grow, provide winter color. Your conifers are likely to be mostly Douglas firs. Salal, Oregon grape, evergreen huckleberry and ocean spray are typical associates on sites tending towards dry. Ceanothus (C. velutinus) and manzanita are found on the hottest, most exposed and/or sandy sites here. Columbia manzanita is so prone to spotting and blackening of the foliage that it is not really a satisfactory ornamental on the whole. There ARE some old ones in local gardens here and there, on rockeries and in other exposed positions. Often when examined up close the foliage is infested.

Indian plum is characteristic of floodplains and other places where soils become damp in winter. Red elderberry also prefers it moist and fertile, the lush look of many deciduous trees and shrubs and woodland wildflowers hints at what they want.

All occur on sites less than perfect in nature, and can be readily coaxed into growing in gardens made not on sites they would be found on spontaneously using simple tricks like watering a little in summer or planting against a south-facing wall.

Going on walks and looking at nearby undeveloped lots, uncleared portions of city parks and other places where there is still natural vegetation and noting what grows where could be highly instructive. Keep soil fertility and moisture regimes in mind, as well as light exposure. You can actually analyze a site using the native plants that are growing on it.

Bellevue is actually one of the places where large, old wild deerbrush can be seen right in town. 405, north of 522 used to have them fringing the verge between the madrona forest (another indicator of warm, well-drained sites) and the freeway, where they would get the heat radiating off of the verge. This population was hammered by the 1990 winter (yes, sometimes even native plants freeze) and then WSDOT put up noise abatement walls where they had been. Few can be seen there today. However, there is a south-facing church parking lot (sorry, don't remember name or address) with nice big ones growing along the bank above it. Another place where one is perched above a parking lot is the tiny viewpoint park east of 405 and north of 522, near power lines. You park and walk a short distance through a forest remnant to a get a view of commercial building rooftops and parking lots. On a nice day the heat rising from below and greeting you right where you encounter the shrub, at the top of the dropoff is quite noticeable.

Hit a library for WILD PLANTS OF GREATER SEATTLE for more information about local presence and other characteristics of specific native plants.

I like the look of patches Mahonia nervosa and the Evergreen huckleberry.

These often grow with salal in the wild. If you can wait decades the huckleberry actually gets quite tall and would be good for screening, having a similar texture to box (one of its common names is box huckleberry). Another tall one is coast rhododendron, but a little of such a large leaf in a planting goes a long way.

White forms of redflower currant develop rapidly and show quite well against dark green conifer foliage.

Here is a link that might be useful: Burnt Ridge Nursery and Orchards - NW Native Shrubs

bboy: I will have to go check out the wild Bellevue deerbrush. Sounds great. I'll get the guide you recommended as well. And thanks for the link to Burnt Ridge.

Since I have wild madronas, salal, and Mahonia aquifolium growing in my back yard, I believe I can conclude that I've got a dry, well-drained site. I think I'll try filling the important areas with ocean spray, and experiment with some of the others at my leisure.

mdvaden: I like that combination too; last week I planted the last of my evergreen huckleberries right next to a patch of wild mahonia.

Ocean spray is often seen coming out of salal in the wild.

Arctostaphylos columbiana does occur frequently as an understory shrub, especially in the eastern foothills of the Olympics, usually in open pine forest. However, it always looks better in the sun.

Not quite native, but you might also consider Calycanthus occidentalis.