Check out the article at: http://www.aschoenbart.com/2016/05/4-tools-to-schedule-communication.html
I have personally used Remind and Tweetdeck. Both are great tools to schedule communication, If I could add one to the list, I would add Blogger. I use blogger to automate my posts to Facebook, Twitter, and my website. I can also create posts in advance and schedule them to post at a later time.