Robinhood - Free stock trading service.
QuantConnect - QuantConnect provides a free algorithm backtesting tool and financial data so engineers can design algorithmic trading strategies. We are democratizing algorithm trading technology to empower investors.
Trigger Finance - IFTTT for the stock market
Quantopian - Your algorithmic investing platform
SysGears Grain Framework - The simplest way to start investing.
CloudQuant - Crowd based algorithmic trading development and backtesing for stock market trading.