TradeKing offers low commission of $4.95 a trade with no account minimums. The site layout is simple and should be easy for those new to online trading to navigate and place orders. They also offer extensive educational resources including webinars and videos for those looking for trading insight. Their customer service is highly rated and they have a trading network for you to learn and discuss trading with fellow traders.
Interactive Brokers offers access to over 80 markets and ultra low commissions. They are geared toward serious traders looking for access to almost every market globally. Almost every serious active trader is familiar with the name.
MB Trading also offers ultra low commission and low account minimums. They are a good choice for those looking to get started in active trading.
Scottrade - Online Trading, Online Investing, Discount Brokerage, Stock Trading, Stock Research, Online Broker, Retirement Investing, IRA
TD Ameritrade - Online Stock Trading and Investing
Charles Schwab - Investment Services Including Online Investing