One of most useful sites I’ve ever come across for learning mac keyboard shortcuts is danrodney.com. There, you will find a very well laid out collection of shortcuts and explanation of various menus you might find on your mac. As well as gestures, tips & tricks, recommend apps, and more. If you’re trying to become more of a power user on your mac, this is definitely a website you should bookmark and visit once in a while to brush up on your skills.
You can visit the Dan Rodney website here