I'm probably one of the few actual traders on here. I rarely hold anything longer than a few weeks and I trade almost purely on technicals.
I've been following the markets for over 10 years now and absolutely love how unpredictable they are.
Before you actually start trading, I would take the time to read, paper trade, and define your rules. You need to figure out what type of trader you are, if that's even for you. If not that's perfectly ok too.
The reason I say that is because each broker has a different personality as well. I would be extremely cautious trying but the top few brokers if you actually do intend to trade.
There are plenty of main stream brokers for investors: TD Ameritrade, Charles Schwab, Scottrade, Fidelity, etc etc. Those are all great brokers for investors. Their focus is on research reports and holding stocks for a longer period of time. One of the reasons traders shy away from these brokers is because they don't exactly provide you with the best execution price, or the best fees.
Luckily, there are also a handful of good trading brokers. Some of the top rated ones are: Tradestation, Thinkorswim, and Interactive Brokers. I'm personally with ThinkOrSwim. I don't think they provide any research reports or anything like that... but nor do I ever care to look at one. The common themes between these brokers is that they all have their own independent platforms (ie not web based). They also generally have cheaper trades and better execution prices.
I do recommend reading and learning as much as you can before diving into the markets. The most important thing to understand as a trader is risk management. Trading is very different from investing, in that you don't just buy something and check the stock price 5 years later.
I whole heartedly recommend reading books #1-11. They are essential to every trader (I couldn't have come up with a better list myself).
http://blog.stocktickr.com/2007/07/09/what-books-do-successful-traders-recommend/
You can feel free to PM me if you have any more questions, or post here.