You too can join the fight. If you have a server that runs PHP, the script you need to run can be found here.
What will this type of attack do? Well, no one is quite sure. Probably take the corrupt Iranian government off the internet. It probably won't get the elections overturned, or make cupcakes come out of Ahmadinejad's ass. But, hey, its something.
Also, there will probably be lulz to be had.