What type of homemade or household alternatives can be use in place of expensive reef

So I was thinking it would be nice to have a list of alternative additives, what it does, and what we can use it for as a reference.

I would like to start things off with a nice article I found by Randy Holmes - Homemade Two-Part Calcium And Alkalinity Additive System http://ift.tt/1OxNNxH

made with Baking Soda, Epson Salt and Dowflake 77-80% Calcium Chloride found at Home Depot.