If your parish young adult ministry is too small to facilitate your own community service project, consider teaming up with other parishes or religious groups in your community for a collaborative service project at a local community and/or social justice organization.
And to make further connections to social justice issues — ask a young adult in your community who works for or volunteers with a social justice organization (this might be where you volunteer), to speak at a young adult Social Justice Education event where s/he shares about her/his social justice commitments, and how they relate to her/his personal faith and the broader church community. Invite the audience to engage in a subsequent discussion about that social justice issue.
You might combine these two events — education and service — into a day-long experience or social justice retreat.