1) Dieffenbachia or Dumb Cane, like you said
2) Caladium cultivar, commonly called Angel Wings or Elephant Ears. The vine growing behind it is a Pothos.
3) Looks like another Dracaena, only variegated (meaning it has striped leaves). The plant growing below it as a groundcover in the pot is wandering jew, in the genus Tradescantia.