Hi,
That is a tall order. By the time I finish my response, vagrant or some other Portlander will likely snipe me on the post! I was born in the Portland area, grew up in Seattle, and have lived the last 20 years in Vancouver (just north of Portland). Here is the "short" list of what immediately came to mind.
Portland:
Cannon BeachEcola State Park
Oswald West State Park/Short Sands Beach
Coast highway south to Manzanita
Columbia Gorge:Historic HighwayWomen's forum overlook
Vista House
Latourelle Falls
Wahkeena Falls
Multnomah Falls
Oneonta Gorge (shorts/sandals recommended for wading)
Horsetail Falls
Bonneville Dam (Oregon side)Sturgeon pools
Washington Highway 14Cape Horn
Beacon Rock State Park
Bonneville Dam (Washington side)Powerhouse
Fish ladder viewing room
Hood River -- wind surfers
Mt HoodTimberline Lodge
Cloudcap chalet (remote on NE side)
Smith Rocks -- Red rock formations, rock climbers up close!
Mt. St. HelensJohnson Ridge Visitor Center
Windy Ridge overlook (remote NE side)
Seattle:
Seattle Center/Space Needle
Pike Street Public Market
Seattle Art Museum (downtown and Volunteer Park locations)
U.W. Arboreteum
Gas Works Park (Lake Union)
Seattle waterfront
Any Puget Sound Ferry
Mt. Rainier Paradise (most visited/photographed)
Sunrise (very dramatic on East side)
Mowich Lake -- Day hikes to incredible scenery Eunice Lake
Spray Park
Snoqualmie Pass east to EllensburgVarious day hikes to wonderful places
Great view of the Mt. Stuart peaks on the east side
Stevens Pass east to Wenatchee Various day hikes especially out of Leavenworth
Leavenworth (faux Bavarian village)
Olympic Peninsula (ferry ride) Port Angeles
Hurricane Ridge
Lake Crescent
Dungeness Spit
Pt. Townsend
There is much, much more, particularly from a photographer's point of view. Enjoy!
Steve