We discussed this a bit on the Cascade board and the consensus was that as bicycles are legally allowed to travel on a shoulder, when a shoulder exists it is a de facto travel lane for bicycles, therefore as a bicycle if you are traveling on the shoulder you may pass on the right under certain conditions.

RCW 46.61.770
Riding on roadways and bicycle paths.
A person operating a bicycle upon a roadway may use the shoulder of the roadway or any specially designated bicycle lane if such exists.


I won't argue that what is technically legal is always the smartest thing to do, and moving up a few spots at stop signs is a) likely to antagonize motorists and b) make it more likely that you will be hit, so I don't recommend it. Now if there is a lot of standing traffic and you can travel on the shoulder for a long distance, go for it. There are perks to riding a bike and increased mobility is one of them.