Ctrl + C or Ctrl + Insert
Copy the highlighted text or selected item.
Ctrl + V or Shift + Insert
Paste the text or object that's in the clipboard.
Ctrl + Z and Ctrl + Y
Undo any change. For example, if you cut text, pressing this will undo it. This can also often be pressed multiple times to undo multiple changes. Pressing Ctrl + Y would re-do the undo.
Ctrl + F
Open the Find in any program. This includes your Internet browser to find text on the current page.
Alt + Tab or Alt + Esc
Quickly switch between open programs.
Open help for the program you're in.
Ctrl + P
Print what's currently being viewed in programs such as Microsoft Word or your Internet browser.
Ctrl + Left arrow / Right arrow
Move the cursor one word at a time instead of one character at a time. If you wanted to highlight one word at a time you can hold down Ctrl + Alt and then press the left or right arrow key to move one word at a time in that direction while highlighting each word.
Ctrl + Home / End
Move the cursor to the beginning or end of a document.
Page Up / Space bar and Page Down
Pressing either the page up or page down key will move that page one page at a time in that direction. When browsing the Internet pressing the space bar will also move the page down one page at a time.