Simple Anytime Pranks and Practical Jokes
The Practical Pranks section at LumpyPorridge.com offers directions for Car, Computer, House, Food, Money, Office, Party, Phone, and Water Pranks..
There's also a page of Computer Pranks with downloadable programs, such as Mocking Eyes, Slippery Mouse, Buttons, and Virus Installation. (Proceed at your own risk.)
Note: The Email Pranks page did not display any content during my visit.