A great feature is that it lets you create custom lists with the markets that interest you most. You can thus have all the information you want at a single glance without having to jump from one tab to another.
In addition to following your actual investments, you can also follow fictitious portfolios for practice to see how well you would do if you were investing real money. An excellent way to get started if you're new to investing, as you can't lose any money.
StockMarketEyed is very useful for investors and people who play - or want to play - the stock market. Its interface is also very easy to use, even for beginners.
30-day trial period.