If anyone is looking for a good site for online investing, I use www.firstrade.com.
(No affiliation at all, just want to share.) You should research for yourself, but I decided on Firstrade after doing a lot of research. It is not the cheapest, but it is cheap. It is also very highly rated. Finally, it's easy to use. If you don't do a lot of trades, it's also nice because it does not require a certain amount of trades to keep from being charged excise fees.
Hope that helps anyone who is looking to invest online.