Other than sharing our calendars with each other, the best way that my wife and I stay in sync is with Wunderlist. The beautiful task manager offers well-designed iPhone, iPad, Android, Mac and Windows apps, as well as an amazingly powerful website. All stay in sync automatically, and sharing a list with a friend is a snap. We primarily use it for grocery lists, so we share a list for Costco, Target, Trader Joe’s, etc. I’ve got a HoneyDo list ready every weekend. And when we are planning a special event like a birthday party, it’s easy to share responsibilities. You can even add sub-tasks, so the Party City item can break down to balloons, hats, helium, etc. The price? Free. Download it and invite me to a list to try it out. My name is Joe, and this is my website, in case you don’t know my e-mail address.