Robinhood - Free stock trading service.
TradeStation - Whether you trade stocks, ETFs, options or futures, TradeStation’s award-winning tools and...
DataSpark - Get access to exclusive hedge-funds stock research, for free
OptionsHouse - OptionsHouse is an online stock trading platform with an easy-to-use interface.
SparkFin - Learn the markets for free, profit forever.
Questrade - Questrade IQ Mobile is everything you need to trade stocks - right in the palm of your hand.