I have an account at Ameritrade and one at InterActive Brokers. I love both for different reasons. IAB has the lowest commissions but you have to pay at least 10 bucks a month in commissions or you will be docked 10 bucks a month minus whatever you paid that month in commissions. IAB also has a reputation for lousy customer service. IAB really wants active customers and that just might suit you. I think 10k minimum to open for IAB. The commissions are .005 per 100 shares, 1 dollar minimum. They also have a lot of hidden fees like charging you for real time quotes (I just use my Ameritrade account to get that info), real time news, moving money around, canceling orders, writing checks, shorting stocks daily interest and many others. If you are active though it's going to be your lowest cost option unless you are buying boatloads of penny stocks or low dollar plays. I've been with TD for over 10 years and have been happy overall but had I known about IAB I would have just started there. You may want to check out Trade Station, I've never tried but heard great things about their platform. I think they let you trade for 6 months free but after that I'm not sure what the fees are. Share Builder is supposed to be another good low commission house but they don't really appeal to the trader and more the long term investor. I had an account at Etrade about 10 years ago and hated it compared to TD.
That's about all I know