Google this week continued its assault on Microsoft's core businesses with the release of Google Sites, an online collaboration service aimed squarely at Microsoft SharePoint. Google Sites is being rolled into the company's Google Apps online productivity suite and, like most Google services, is being offered for free. (Though you will need a Google Apps account to use the service.)

"Google Apps makes creating a team site as easy as editing a document," the Google Sites Web site reads. "Use Google Sites to centralize all types of information--from videos to presentations--and share your site with just a few people, your entire organization, or the world."

Google Sites is a repackaged version of the Jotspot collaboration platform that Google purchased in 2006. Like SharePoint, it provides a simple way to create Web-based sites for intranets, team projects, schools, and other uses, letting teams of people work together on documents, photos, calendars, and more. It integrates with other Google services, including the Gmail, Google Calendar, and Google Docs services that are part of Google Apps, and Google Picasa and YouTube.

While Google isn't expected to generate a lot of income from Google Sites in the short term, this business has proven to be fairly lucrative for Microsoft: The software giant has transformed SharePoint into a $1 billion a year product, according to Microsoft CFO Christopher Liddell.