Three out of four of Oregon's coastal branches are embargoed at the moment. The A-Line is out of service somewhere west of St. Helens on account of a washout and lack of traffic in Astoria. In Astoria there is the aforementioned waterfront trolley and boardwalk. Also in Astoria is the old SP&S brick station that was used for the Lewis & Clark passenger excursions a number of years ago. There is also a steam engine there being restored, though I don't have more information handy at the moment. It's located towards the west end of town near the Red Lion Inn. I don't recall if there are any remnants of the trestle over Youngs Bay but a good chunk of the right-of-way of the Seaside Branch is visible along Highway 101 towards its namesake city.
The Port of Tillamook Bay Railroad is also embargoed due to a washout dating back to last December. The line is the topic of debate in the Oregon legislature and its future is much up in the air. The museum that operates in Tillamook is isolated now because of the washout. I believe the Great Northern F-unit pictured on their web page is owned by Doyle McCormack and is also stuck out there pending a truck ride back to Brooklyn.
The Portland & Western's Toledo Branch is the only active line to the coast at the moment. I'll have to dig to find operations information for you. It is freight-only.
The Coos Bay line was embargoed a year ago by RailAmerica and the STB has since ruled this to be an illegal abandonment. A forced transfer is being proceeded with by the Oregon Department of Transportation to acquire the line and name a new operator on behalf of the state.
The best railfan experience is in the Willamette Valley. Spend a day riding the Portland Streetcar and Tri-Met MAX and you'll see so much of the city. The new DMU-equipped WES line from Beaverton to Wilsonville is slated to open in February should Colorado Rail Car not further screw over Tri-Met. There are also a number of railfan spots throughout the metropolitan area that are worth checking out. My favorite is watching the action across the river from the 30th floor of the Bancorp Tower in the
Portland City Grill. If being trackside is preferable there almost always seems to be a railfan crowd hanging out at the Vancouver (Washington) Amtrak station, just up I-5 from Portland.
Of course, another great option for a train ride is a day trip on Amtrak in to Washington. Even if you don't get to stay long the train trip alone is worth the fare. There are plenty of round trips from Portland to Seattle and one could even turn back at Centralia without missing any of the experience.