I really like the TD Ameritrade ThinkorSwim trading platform.
They offer a great charting software for free with an account. You get quality charting with just about every study you can think of to analyze stocks with. You can also trade directly from the chart.
You can bring up multiple charts over numerous monitors which is great for active traders. They also offer news, a scanner, option analysis.
The only thing I do not like is the commissions if you are an active trader. If you are a swing trader or rarely trade then even that is not a big deal. The commissions are competitive for the tools you get.