For many investors using a stock chart when interested in indexes like DJIA or S&P 500 is an essential thing to keep an eye on daily movements of stocks and current market trends. However these days you do not have to have complex expensive software or data feeds to get access to this data.
There are websites online which feature an array of investing tools, like a stock chart for the dow jones. A popular one can be found here DJIA chart. Also on this site you can get a real time S&P 500 chart which allows you to see the movement of the index in timeframes from one minute to daily and weekly.
Having live data can help you when you are active in the markets. If there has been a economic news release which is pushing down stocks you may want to cash in some of your portfolio while you still have profit. Using delayed data has disadvantages in that by time you see how the markets have reacted to any data the DJIA or S&P 500 could be further down and if your stocks are within these indices then you could have missed an opportunity to get out with more profit.
Make sure you visit and bookmark the above charts if you are active in stock trading, they can surely help as a guide to how the market is performing in real time.