Not sure if this qualifies as anti-war, but it is anti-GW:

The Wartime
President Song!

My old man, he had oil...
so I'd never have to toil !
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !
My old man, made a call...
so I didn't go to 'nam at all!
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !
Did my time in the Guard...
Went AWOL... It wasn't hard!
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !
DUI? I made bail...
Then Daddy sent me off to Yale!
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !
We won the war, so wave the flags...
just ignore those body bags !
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !
I'm in charge. I'm the Prez...
Cause I do just what Cheney says!
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !
I'll do fine in the end, cause
Halliburton is my friend !
With a knick-knack, bomb Iraq
all your money's spent...
I'm a wartime president !

Got this from over at www.onegoodmove.org