Volunteering centered on ideas often gets expressed in a service of some sort. Serious leisure examples are legion: pro-bono legal service, volunteer consulting, volunteer retired business people advising on business, and political party volunteers working on strategy or policy. Not conceivable as a service, however, is advocacy volunteering (including protest activity), which nonetheless requires manipulating ideas, in this instance, to persuade a target group. Moreover, for those wanting only a limited volunteer experience, any of these could also be carried out as leisure projects. Finally I could think of no instances of casual volunteering using ideas, and perhaps for good reason. Casual leisure is fundamentally hedonic and, as such, not idea-based volunteer activity as conceived of here.
It is possible that volunteer work with human-made things is the arena for the largest amount of project-based volunteering. Some material volunteers organize their work for Habitat for Humanity as a project, as do those who donate their trade skills to fix a plumbing or electrical problem at their church, prepare food for the needy on Thanksgiving Day, or help construct the set for a high school play. Examples of material volunteering as serious leisure include: regular volunteers who repair and restore furniture and clothing donated to the Salvation Army, prepare meals for the indigent, and perform secretarial or book keeping services for a nonprofit group. Volunteers providing water filters and electrical lighting to Third World countries are engaging in serious leisure material volunteering, as are volunteer firefighters (when not rescuing people). Casual material volunteering refers to such activities as regularly stuffing envelops for a nonprofit group mailing, picking up trash along beaches or roadsides (could also be classified as environmental volunteering), and keeping the score at adolescent sporting matches.