Portland helmet advocacy is a good scene... encountered it at the Multnomah County Bike Fair last year. Helmets aren't mandatory by law in Oregon so they have a cute program advocating their use.

That said, the bike snobs here in Vancouver are all about not wearing helmets. Those little cycling caps may make you look cool but they won't protect your brain... and I must admit I do feel pretty dorky wearing my helmet riding with the cool kids... but my head will be okay if anything happens, so I feel a bit better bombing down main streets.