Swarm Portland works to create more urban bee habitat and backyard pollinator refuges. Planting bee-friendly gardens also attracts butterflies, hummingbirds, and beneficial insects.
A key to creating a refuge for bees is to avoid using pesticides, these chemical substances don't discriminate between good and bad insects and they're lethal for bees. Some commonly used pesticides called neonicitinoids are "systemic," which means once they're applied to plants the chemicals remain active over time so there is no safe time.
Swarm Portland's hex shaped Pollinator Planters can highlight pollinator patches in your garden. More info here: http://swarmportland.org/products/hive-bee-bed
Bees need water and if you have a bird bath, remember that bees need stepping stones. Refresh the water regularly, and especially on very hot days to avoid evaporation.
While honeybees attract a lot of attention, native wild bees are very important to our food system and environment. Local bees like native plant species, and we can plan gardens that provide forage for pollinators throughout the growing season.
Below is a chart with some suggestions for bee-friendly plants, and you can check with your local beekeepers groups and nurseries for more information about your location (source: NW Edible).
The Bee Haven at UC Davis has created this list of plants that includes info on which ones are best for pollen and nectar (many have both).
Additional online pollinator garden resources:
NASA Honey Bee Forage Guide for Oregon
Pollinator Conservation in Portland metro area