From Transit.Wiki

TriMet (Tri-County Metropolitan Transportation District) provides local and regional transit in the Portland metropolitan area, covering parts of Multnomah County, Clackamas County (Clackamas, Oregon City, Happy Valley, Lake Oswego, Milwaukie, West Linn), and Washington County.

TriMet operates buses, MAX Light Rail, and WES Commuter Rail. TriMet connects with Portland Streetcar (run by the city), Amtrak trains, and C-Tran buses to Vancouver, Washington.

Agency web site
Lost and found
Upcoming service changes
Board of directors

Bus routes
MAX Light Rail
Blue Line — Hillsboro - City Center - Gresham
Red Line — Beaverton - City Center - Airport
Yellow Line — Expo Center - City Center - PSU
Green Line — Clackamas - City Center - PSU
Orange Line — City Center - PSU - Milwaukie
WES Commuter Rail
Fleet info, service change list