One is stockcharts.com devoted to technical analysis of stocks. They have lots of free resources like a weekly newsletter and great stock charts, as well as some paid services. I use only the free ones and use their charting regularly

A very nice stock charting software that is free to use for as long as you like is at quotetracker.com – I have used it for nearly 10 years and it can build charts that are simple or very advanced. You’ll need a connection to a data feed for the charts; some are free and some can be expensive.
The software was originally developed independently but was purchased by TD Ameritrade brokerage about two years ago, so if you have an account with them, you’ll also get free stock charting data to run the software. The software has a ton of features, and can be a little intimidating, but I use it daily and like it a lot.

For something a bit simpler, another way to go would be an all in one free applcation like the-market-toolbox.com – there again are sections that are free and some paid services, but all the basics like charting, research, and trading ideas are all free. They have you register to download the software and they will likely start sending email, but the list is easy to unsubscribe if you choose.

There are many choices available in the market that are free or very cheap and you only need to decide what sort of trading or investing appeals to you in order to narrow things down. An article I came across recently may help you to answer that question : http://preview.tinyurl.com/ahoacy
References :
10 years of active online trading.

http://stockcharts.com/school/doku.php?id=chart_school

http://www.quotetracker.com/

http://www.the-market-toolbox.com

http://www.fxstreet.com

http://www.tdameritrade.com