When it's rainy everywhere else in the Northwest...
We went here when another camping trip was rained out in spring. We looked on the map and it was the only dry spot we could find within a few hours of Portland. It was a nice last minute trip, and we easily found a spot without a reservation. The sites are priced by popularity, but upon arrival, we actually preferred one in the second tier instead of the priciest (although we would have paid the extra $5 had we loved one of those instead). There was a short walk from our site through the blackberries to the riverfront, a great place to enjoy a morning coffee. There were clean bathrooms and showers and within the park there is a protected beach swimming area. It looked like there was also a large group sent site off to the west of where we were staying. There are lots of touristy things nearby, like visiting the Maryhill Winery, the beautiful Maryhill Museum, and the Maryhill Stonehenge (all with stunning views). Due to its location, it was quite windy, so don't forget your stakes!