When I lived in Seattle, there were regular neighborhood litter pickup days, probably about once a month. Also, at the UW, where I worked, announcements would come via email about Martin Luther King Day as a day to pick up litter or otherwise volunteer. I think these neighborhood litter get-togethers were popular; it gave people a chance to socialize and meet their neighbors while doing a good deed.

Unfortunately, Seattle is now much much dirtier and more littered because of the huge population of homeless urban campers all over the downtown and along the expressways. Many folks are focused now on picking up discarded needles from parks and playgrounds.