For those of you hesitant to try crack or crystal meth, I just discovered an equally addictive pastime you might consider. The "Planarity Flash Game" presents a network on-screen and invites you to reposition the nodes so that there are no crossing edges. For example, can you see how to uncross the edges in the following network?
After you uncross all the edges in one network, the game presents you another, more difficult network. If you like networks, it's hard to stop!
Thanks to Eszter on SOCNET for sharing this.
BTW, playing this game will give you a lot more appreciation for the complexities of network visualization.