1) Make me a simple jQuery program that makes some text appear and disappear when I click the "appear" and
"disappear" buttons.


2) Make a simple jQuery program that has a table that disappears when I hover over it.


3)  Make a simple jQuery program that has two pictures.  When I hover over the picture,
I see a Luke.  When I don't hover over the picture, I see a Darth Vader.

There is a too complicated example, that you could simplify, at 
http://stackoverflow.com/questions/540349/change-the-image-source-using-jquery