VolunteerMatch - VolunteerMatch strengthens communities by making it easier for good people and good causes to...

Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

Golden Volunteer App - Golden is no ordinary community service app or volunteers app. Create Golden Moments by searching volunteer opportunities. Go from Volunteering to Volunteered.

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

HelpStay - HelpStay Exchange

Bigtent - BigTent is a web-based organization and communication portal for groups.