My mom - at least once a week, usually more, plus a few emails about various things.
My dad - once every few weeks, usually short calls. Neither of us are phone people, so we're both ready to get off the phone after a few minutes.
DH talks to his dad maybe once or twice per year. DH talks to my parents more than he talks to his own father. His mother passed away years ago, sadly, as I know he had a better relationship with her.