Windows only: Keyboard shortcuts are great, but copying and pasting text could be even faster than it is. Free app AutoClipX automatically adds any highlighted text to the clipboard, and pastes with a single click of the middle mouse button.
Copying and pasting text with the keyboard isn't slow by any means, but if you do it a lot, it could get annoying hitting key combinations all the time. AutoClipX makes copy and pasting just about as simple as it could possibly be: you don't have to copy text at all (since AutoClipX automatically copies anything you highlight), and pasting is just a matter of hitting the middle mouse button. The app actually has quite a few settings — like setting a delay to how long you want text to be highlighted before it's copied, or assigning a hotkey to enable and disable AutoClipX, but overall it's an extremely simple program. Hit the link to try it out.
AutoClipX is a free download for Windows only.