This doesn't seem like much but it does several things,
Shows the world that a lot of people here in the US oppose the murderous bush regime.
Pressure our elected officials to stand up to the neocons trashing our fine country
Remind all those here in the US not to give up hope, that there is still strong opposition.
Show our friends in the armed services that we haven't forgot them
At least show up for the march. It's your duty as a decent human being.