Stargate SG1 did this for a time, unofficially, while they were in dispute with the SciFi channel. Those episodes were easy to spot as 1) they were released before the end of the show's first airing (impossible for anyone without insider access) 2) they were of dvd quality 3) they did not contain any commercials, broadcast indentifer overlays, or editing marks and 4) sometimes contained the editing marks that are never broadcast.
Its SyFy now