The following organizations offer solid mitzvah project opportunities:

Jewish Coalition for Service: Umbrella agency for social action volunteer service opportunities around the world. http://werepair.org/

Areyvut. Trains and partners teachers and schools in how to do social action, also lists many ideas and methods for mitzvah projects. Areyvut.org

Mazon: A Jewish Response to Hunger is dedicated to supporting soup kitchens and food pantries; many families give about 3% of B-Mitzvah party costs to this effort. Mazon.org

United Jewish Communities: Look for their page that lists adult and youth philanthropy initiatives throughout North America. UJC.org

The Coalition on the Environment and Jewish Life. Workshops, activism, and studies. COEJL.org

The Jewish Fund for Justice fights the injustice of poverty, assists grassroots organizations and offers programs to help religious schools teach about poverty and justice and to develop tikkun olam projects. Also maintains B-Mitzvah philanthropic bank accounts for youth, with guidance for giving. JFJustice.org

Just Give: Over 850,000 opportunities to support and learn about good causes. Justgive.org

The Shalom Center: Offers a religious school curriculum focused on environmental issues geared to bar/bat mitzvah and beyond, full of ideas for action and grounding in Jewish sources, creative learning opportunities. ShalomCtr.org

Network for Good: Thousands of opportunities to donate your time, skills or money sortable by zip code. Networkforgood.org

Second Harvest: Encourages donation of left over food from parties and links to local food rescue organizations that will come and collect directly after your simcha. Also cites poverty statistics by zip code. SecondHarvest.org