Google non-profits in your area.
They have things you could do, from redesigning thier website to helping implement a curriculum, like west seattle’s very own community service/snowboarding youth program, http://www.theserviceboard.org or if you’re into photography, maybe http://www.youthinfocus.org is your thing. TeamRead, http://www.acrs.org, etc.. Find something that mirrors your passion or conversely, something that you would never think to do in a million years and broaden your horizons. As a senior, it’s never too soon to get ‘free’ experience in a field of interest or connect with someone who can mentor you or provide you with a letter of recommendation.