Opening another front in its war with Microsoft, search giant Google will begin offering a collection of web-based productivity tools. A page describing the offering could be found at on Sunday.

The tools include e-mail, instant messaging, calendaring, and web-page building applications. While the offerings run on Google’s servers, customers will be able to offer the tools as if they were their own.

The web page states that Google is seeking beta testers for its offering, which is customizable “with your branding, color scheme and content through the administrative control panel, and with no hardware or software to install or maintain.”

The move to offer “Google Apps for Your Domain,” follows Microsoft’s move in February to begin a beta test of “Office Live Essentials,” another hosted web services offering.

Google’s move, however, is one step short of a direct challenge to Microsoft’s Office suite of desktop productivity applications. Microsoft has been reluctant to offer web-based versions of those applications, which crank out much of the software giant’s profits.

Google, however, seems to be tiptoeing towards such an offering. It already offers a web-based spreadsheet application. Its acquisition of Writely earlier this year also gives it a web-friendly word processing offering.

A premium offering may be on the way as well. A web page describing the service stated that “[i]f your organization has advanced needs not met by this free service, let us know and we’ll get in touch when a premium service is available for your organization.”

The Mountain View, California, company is also experimenting with desktop software distribution. It’s Google Pack offering combines Google Desktop, Toolbar, Google Earth, Picassa photo organizing software, and other free offerings.

Many have speculated that Google may one day begin distributing open-source desktop productivity software such as Open Office.

Google began offering a server pre-loaded with its search software, dubbed a “search appliance” that customers could plug into their corporate networks two years ago.

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