All baryons — protons and neutrons included — are each made up of three quarks. Antimatter baryons also exist, which are made of three antiquarks. These include antiprotons, which have a negative charge, and antineutrons which are neutral. Since antimatter is destroyed on contact with matter there aren't many of these antiparticles around.
Exotic baryons of exotic types have been proposed but their existence is completely unproven.