The Montley Fool
This is another great site about investing, which contains useful material for both beginners and advanced investors. To start with, it contains the most current market news. Furthermore, it has a nice section called How to Invest, where you can find all you need to know and more. Basically at The Montley Fool, you can find all the same things as you can find on investopedia.com, however, the site fool.com contains more commentaries of real investors and has a nicer interface. This site is highly recommended for beginners. Also it has a nice service of brokers, which can be used by advanced investors.
This site has a very simple interface and very few features. However, you can find valuable articles about stocks, bonds, mutual funds and techniques how to find successful stocks.
Investopedia.com can truly be called an online encyclopedia. You can find basically everything you need to know about the basics of investing on this site starting with tutorial articles ending with a free investing. This site can also be useful for experienced investors, because it has many articles for them too. Due to an easy to use interface, great tutorials and a nice online investing simulator, this site should be a one of the priorities for beginner investors.
News of the Market
You can find all the news of the market here:
1) Market Watch;
2) CNN Money;
5) Stocks and News.