There's a handful of shops on the north Oregon coast that do rentals- Cannon Beach surf is a cool little family run place- They rent all the goods in the summer- not sure about his rental biz this time of year though. There's a couple of shops in Seaside too. Personally I like Seaside surf- they gave me a good deal on my last new stick plus there's a couple of hotties working there- because, you know, that's important too.
Oh if you're in Portland-proper there's Gorge Performance. They have a big rental selection and actually let you test drive new board models.
And yeah- someone mentioned earlier about the winter swell never dropping below chest-shoulder high here- that's the truth. I don't think I've surfed in anything smaller that 4'-6' since Xmas. And even at the most 'popular' breaks here you can get solitude this time of year. Last Friday it was me and my buddy and one other dude in the water at what is arguably the most popular spot on the north coast (Short Sands aka Oswald West aka Smuggler's Cove.)
Granted, it was 6-9' and thumping and a biyatch of a paddle.