R. Webster West has created an
interesting demonstration of conditional probability.
How it works: You can move around the events A and B and see how the sets and probabilities to the right change.
The set which is being shaded may be selected to the right as well. Conditional probabilites are given below the Venn diagram.
(If you are viewing this from behind a firewall, chances are that your webmaster has configured your security so that JAVA functions only on your intranet, and not across the web. So right now you are looking at a gray square, or maybe not even that, which isn't nearly as entertaining as the actual applet.)