According to our forex broker review, Gain Capital and Oanda come out on top.

Gain Capial has set a high standard with trailing stops. The trailing stop can only be entered as a separate order. Once the investor is in an order he can enter his trailing stop limit in pips to trail the market the distance the investor has set with the closest distance the investor can go being 10 pips.  Gain Capital also has a facility whereby a trader can download 5 years of tick data on the 6 major currencies.  In addition, an investor can also download a free DDE application whereby he can obtain live quotes.  

While most brokers allow only the standard ($100,000) or mini ($10,000) lot size, Oanda gives traders the ability to trade any lot amount.  Another attractive quality is that has its own user forum.  In addition, Oanda has the capacity to have multi-denominated sub accounts other than in USD with no minimum deposit. The different currency accounts available include AUD, EUR, JPY, GBP, CAD & CHF. This allows the user to transfer between their primary account and their sub account easily, with the only restriction being that the investor cannot externally withdraw funds from a sub account, and withdrawals must come out of the primary account only.