On the local level the San Mateo County Genealogical Society has numerous opportunities to contribute. You could join the indexing team onsite at the Colma Historial Museum as they index the Mortuary Books of Valente, Marini, Perata and Co. Or, if you'd rather work in the southern part of the county, there are a couple projects that we'd like to start at the San Mateo County Historical Association Museum. We also have an opportunity to work on a project from home. Contact firstname.lastname@example.org if you would like to volunteer.
Another alternative is share your genealogy online. Whether it is in a blog or on a website, a family tree or a story or just a great genealogical find, sharing with others is not only satisfying but also a great way to pay back the genealogical community that shares with you.