CMC appears to be the way to go, with no brokerage for online trades on US, UK, or Japanese markets. Though it appears that IG is also offering this. The custody and subscription fees need to be looked at, though - 0.5% p.a at CMC, $50/quarter at IG - as does the FX conversion charge.
Don't take my word for it, though - go digging for yourself and verify the information.
PM8 Price at posting:
$1.82 Sentiment: Buy Disclosure: Held