Sagebrush - Artemisia spp.
Another favorite of mine for silver color: A. caucasica, 'Silver Spreader', which is only 6 inches high and a good groundcover, or A. ludoviciana albula, 'Silver King', which is 2-3 feet high. Artemisias include the Wormwoods (A. absinthium) and Tarragons.
Snow in Summer - Cerastium tomentosum
Good groundcover that blooms massive tiny white flowers all summer long with silver leaves. Hence, it's name. Plant where it can be mowed or sheared back in winter for revision in spring. If any bare spots show, simply sow seeds in fall or early spring. Can be started from seed or plants. Grows 6 inches high and spreads quickly.
Hen and Chicks - Echeveria secunda
My Mom called these, *chicken n' biddies*(old southern name); you may know them as *Hen and Chicks*. We always had these in our yards wherever we moved. These succulents offshoot profusely, probably, hence, the name. Nice 4 inch wide rosette shape, good in rock gardens, slopes, or dark spots where the silver color can be contrasted. My favorite for it's grey-silver color is the E. secunda, followed by the E. s. glauca.
Lambs Ears - Stachys byzantina
Not to be confused with 'Bunny Ears' (Opuntia, a cactus): Good edger next to reds or vibrant greens or purples. Nice fuzzy silver gray leaves. Not frost tolerant, but will revive after a frost. 'Silver Carpet' is best choice for no flower spikes which can detract from plant.
Bush Germander - Teucrium fruticans
'Compactum': nice silver-white undersides with grey-green above, deep blue flowers all year long, nice 3 foot high shrub. Great with a Mediterranean theme, very drought tolerant. Takes poor soils. But NOT poor draining soils - wet conditions will kill this shrub.