I've used ZeroClipboard in a couple of my projects which allows me to provide a clickable object which copies text of my choosing into the client's clipboard. I usually use copy and paste keyboard shortcuts, but there are times when it's nice and more effecient to have a click-to-copy button.
Get the files
wget https://github.com/zeroclipboard/ZeroClipboard/raw/master/ZeroClipboard.swf wget https://raw.github.com/zeroclipboard/ZeroClipboard/master/ZeroClipboard.min.js
Import the files and create the basic structure