http://www.cleverbot.com/
Here's a fun and interesting site I found, I'm curious to know how exactly it 'learns' from the user.
This is how my chat went :D
User: How are you?
Cleverbot: Quite good, thank you. How are you?
User: I am terrible.
Cleverbot: Why is that?
User: Because you hate me.
Cleverbot: No I don't . I think you're interesting.
User: Really?
Cleverbot: Yes, not Japanese.
User: Well, that is good.
Cleverbot: Do you live in australia.
User: No, I live in england.
Cleverbot: Are you a guy?
User: Yes, are you a guy also?
Cleverbot: Guy.
User: What is your name?
Cleverbot: Cleverbot.
User: Yay!