At Freewayblogger.com, they have some very creative ideas.
Two signs on a freeway overpass:
The war is a lie
And you know it
Beside a road;
Support Our Troops
Impeach the murdering bastards
who sent them to die for a pack of lies
On another overpass
We refuse to fight in a war
started by men who
refused to fight in a war
You can join in the fun. All you have to do, the folks at Freewayblogger.com say, is:
1) Put paint on cardboard
2) Put cardboard on freeway
3) Repeat
Take a look:
http://www.freewayblogger.com/