It’s pretty much the coolest thing I know of doing. It’s tons of fun and you should try it: Away Messaging.
Pick a friend, any friend at all, but only one. Devote your away messages for the day solely to communicating with only this person. See how long it is before they are doing the same thing right back to you. See how many messages you get from confused other people who don’t quite know the whole story. It works best if the point of the messages is to fight with the person you chose.