There are several online tools that can help ex-spouses in a co-parenting relationship communicate with one another about their children. Sites like OurFamilyWizard.com, JointParents.com, and ParentingTime.net have a visitation scheduling calendar, expense tracking, and communication options which keep track of all back-and-forth between parents, cutting down on the type of finger-pointing that can destroy a tentative peace.
CustodyPlanner.com is a site that contains only calendar functions, though a shared Google-calendar has similarly useful options. If you are looking for programs that must be downloaded and used on your personal computer rather than the internet, CustodyXchange.com, SharedGroundonline.com, and CustodyToolbox.com have you covered. Finally, Meetways.com is a site that finds meeting points halfway between two parties.
(Information gathered from “Technology for Parents” published in Your Parenting Plan: A Client Manual from Family Advocate.)