Google (NASDAQ:GOOG) launched Google Finance, a product that offers "information about North American stocks, mutual funds and public and private companies along with charts, news and fundamental financial data".You can search for stocks, mutual funds, public and private companies, find news about companies and even blog posts, see related companies, company summary and management information.
You can create a portfolio, if you have a Google Account. Google Finance portfolios allow you to keep track of financial information, including how many shares you own and at what price, for up to 200 stocks or mutual funds.
But probably the best feature of Google Finance is the interactive charts, that correlate market data with corresponding dated news stories to help you determine if there is a relationship between them.
Of course, the product is far from perfect if you compare it with Yahoo! Finance: it doesn't have real-time quotes, statistics, SEC fillings, list of competitors, analyst estimates, list of major holders, income statements, option to compare stocks and many other features. So I think Google Finance can't be considered real competition for sites like fool.com or finance.yahoo.com. Yet...
Update: Google Blog says that Google Finance "started as a small project led by a few engineers in Bangalore and later joined by more engineers and finance enthusiasts in Mountain View and New York".