There is one from Des Moines sponsored by Central Iowa Peace and Justice.
http://home.earthlink.net/~ipnet/calendar.htmFriday - Sunday, Sept. 23-25: "Buses from Des Moines for the Peace Demonstration in Washington, DC" departure place TBA. The Methodist Federation for Social Action is arranging for buses from Iowa to join the "End the War in Iraq -- Massive Mobilization" in Washington. Round-trip bus fare not to exceed $110. For more info or to reserve a seat, call Chet Guinn at 515-282-8054 or 515-556-8054.
I also saw online somewhere that there was a bus going from Iowa City. I can't remember where I saw it at though.