Hominoids – all apes. Gibbons, gorillas, chimps, orangs and humans .

Hominids – all modern AND extinct GREAT apes. Gorillas, chimps, orangs and humans, and their immediate ancestors. Not gibbons.

Hominin – Any species of early human that is more closely related to humans than chimpanzees, including modern humans themselves. (At this point, this includes the genuses homo, australopithecus, ardipithecus and paranthropus. These genuses can and do change as various new fossils are found, which either add new genuses, or cast doubt on existing ones. Homo and australopithecus are the two most definite).

Basically, Hominoid is more of a biological reference, while hominids and hominins are more archaeology/anthropology related.