Here's a great Finder feature: "new folder from selection." Try it once and you'll do it all the time. Easier than dragging items to folders.
Quickly collapse all of the folders in a given window, with two keystrokes! Save time and impress your friends. Super easy and fast.
Delete an item from the keyboard! You'd think you'd use the Delete key, but you'd only be half right. The other half involves the Command key.
There's more than one way to do this, but Get Info does reveal the size of an image, in pixels. Rather handy. Try it!
Here's how to know the location of an open document, all with a simple click. Actually, all with a simple Command-click. It's a great feature.
Switch between the Finder's icon and list views with simple keyboard shortcuts. What could be easier than Command-1 and Command-2?
Apple hides your Library folder because they don't want you accidentally messing it up. When you have to get into it, use the Option key and the Go menu.
Add text labels to toolbar buttons, making them easier to identify & easier to click on (because they're bigger). Works in Finder, Preview, Mail, and more.