The only kingdoms that do NOT contain unicellular organisms are Animalia and Plantae. All of the other kingdoms (Monera, Protoctista, and Fungi) contain both unicellular and multicellular organisms. Unicellular fungi are yeasts. Most protoctists are unicellular, but multicellular forms with differentiation (special jobs for different cells) exist and include some algae and slime molds. Kingdom Monera, which includes all bacteria including archaebacteria (also called archae, and considered by many to be its own kingdom or domain), are primarily unicellular but examples of multicellular forms, again with differentiation, do exist. Multicellular bacteria include myxobacteria (very cool -- worth an image search) and cyanobacteria, which have heterocyst cells that fix nitrogen. I do not know of any multicellular archaebacteria.
