Everyone generally is looking for a way to get things done faster. Here is a list of keyboard shortcuts that have been around for awhile, but are still very useful to have on hand. Enjoy!
⌘ Q Quits whatever app is open (First Class, Firefox, Word, etc.)
⌘ W Closes Window
⌘ R Refreshes browser
⌘ L Highlights URL area in browser
⌘ T New Tab
⌘ N New email (when in First Class), new window when using a browser, new Finder window when in Finder, etc.
⌘ Space Bar Opens spotlight to search
⌘ S Save
⌘ P Print
⌘ C Copy
⌘ V Paste
SpaceBar When something is highlighted on your desktop or in the Finder window, you can hit your space bar to preview selected item without actually opening it.
⌘ Shift 4 Takes a screenshot
⌘ Option Escape Force Quit
⌘ A Select all
⌘ Z Undo
⌘ X Highlight selected object to cut and copy. Use ⌘ X to delete the object and ⌘ V to paste it somewhere else.
⌘ + Zoom in
⌘ – Zoom out