Flying/Ghost is immune to Normal, Fighting, and Ground.
Ghost/Steel is immune to Normal, Fighting, and Poison.
Dark/Ghost is immune to Normal, Fighting, and Psychic.
From what I saw, those are the only type combinations (Other than the ones you mentioned.) that have three immunities. There are also no Pokemon with more than three immunities. The only other way that a Pokemon could have three or more immunities is through abilities, such as Levitate, and type adding moves, (I'm almost certain that type changing moves, such as Soak, or type changing items, such as Arceus holding an Iron Plate, will not allow a Pokemon to have three or more weaknesses, as it changes the type, instead of adding one.) such as Forest's Curse.