I've been planning on riding on the Seattle to Portland bicycle ride that happens every July. The 200 miles ride starts in Seattle and takes 1 or 2 days to ride this route to Portland and usually has ~7000 bicyclists.

Some of the places I've cycled:
Vernonia-Banks Trail (actually starts in Manning)
Champoeg Park loop and surrounding farmlands.

Portland Bicycling:
Oregonian Cycling Page
Springwater Corridor
Bicycling around Portland
Seattle bicycling info
Portland's Bicycle Plan and Programs
Portland bicycle routes and other information
Many bicycle links (www.bikelane.com)

Cycling News
VeloNews
Tour De France (2002)
Giro D'Italia