I know some have expressed an interest in alternatives to SB firms to trade the Dow. Well I stumbled across this site today and there seems to be a lot of information here. I have no axe to grind here, as I don't trade the Dow either through spread betting firms or directly in the futures market.
http://www.cbot.com/cbot/www/cont_modular/1,2291,14+478+7,00.html#d
http://www.cbot.com/cbot/www/cont_modular/1,2291,14+478+7,00.html#d