is the one. I have just opened an account there. they seem to be the IB of the currency world. however word of warning they are not CTFC registered, although they are in the throws of getting accreditation. best to have a good read of their site forum, which is quite open.
I researched fxcm, saxobank, dealstation and many others. nothing, unfortunately, touches oanda for the features they offer.
the biggy for me was no set contract sizes. $1 - $10mil. Not in $100k portions like everyone else. fantastic for hedging currencies for us non-millionaires.