Looks like Macquarie might have the cheapest online brokerage for online US trading as far as a Australian brokers are concerned. For larger trades it works out to about 0.16%
They told me today that they can debit any Australian bank account and then transfer funds to US bank account ready for US trading.They also recently added US online option trading as well.
Product profile Minimum trade amount Online: Nil Using a Macquarie adviser: US trades:Nil International trades (outside of the US):US$25,000 Fee for each trade - online US $39.95 for trades less than US $25,000 An additional US $39.95 for each US $25,000 amount over US$25,000 ** Fee for advisory services* US$125.00 per trade or 1.50% of each trade value, whichever is greater International trades outside of the US: minimum US $250.00 brokerage. Administration fee US $80.00 pa