Hemicelluloses, comprising the non-cellulose cell-wall polysaccharides of vegetative and storage tissues of annual and perennial plants, represent an immense renewable resource of biopolymers. They occur in a large variety of structural types, divided into four general groups, i.e., xylans, mannans, mixed linkage β-glucans, and xyloglucans. The presented review summarized recent reports on hemicelluloses, including the arabinogalactan from larch wood, focused on new plant sources, isolation methods, and characterization of structural features, physicochemical and various functional properties. Attention was paid to derivatives prepared from these polysaccharides and to application possibilities of hemicelluloses or hemicellulosic materials for food and non-food applications, including the production of composite materials and other biomaterials.