Google acquired many of the Web-site tools when it bought a Silicon Valley startup, JotSpot, last year. The tools are the latest addition to a bundle of applications that Google offers to consumers and businesses as alternatives to similar products sold by Microsoft Corp., one of Google's fiercest rivals.

Google's latest service represents a challenge to Microsoft's SharePoint, which charges licensing fees. Google is unveiling its alternative just a few days before Redmond, Wash.-based Microsoft hosts a SharePoint conference in Seattle.

While Microsoft's programs typically are installed on individual computers, Google keeps its application on its own machines so users can access them from anywhere with an Internet connection.

By gradually introducing free versions of word processing, spreadsheet, and calendaring programs over the past two years, Google has been threatening to siphon revenue away from Microsoft, which makes most of its money from software sales.

Microsoft, in turn, hopes to take a bite of out Google's bread-and-butter in online search and advertising by buying Yahoo Inc. for more than $40 billion.

Google says more than 500,000 companies, government agencies and schools use at least some of its applications. The company won't say how many of those organizations subscribe to a premium version of its software suite, but the fees haven't made much of a dent at Google so far.

Last year, Google's software licensing and other products generated $181 million in revenue while $16.4 billion poured in from advertising.