I've always found "The Brain" to be the most useful. :-)
Really, if you practice, do WAY more problems than you are assigned, you will find yourself needing very few hints in very little time.
I need a quick reference to math rules that I can refer to when solving algebra and other math problems. When I'm working on algebra problems I find myself having to do google searches for rules on algebra and rules on math that I need to perform while working on algebra problems. Anyone have a link or maybe know of an iphone app or somthing?
TKHunny's advice is normally worth listening to.
But if you want a reference card you'll have to tell us your level of study and what you want to be on it. Even better, why not write these results down yourself the first time you look them up?