The limited Technical Preview, as Microsoft is calling the program, is accessible through the company's Windows Live SkyDrive storage portal, Microsoft said.
Invited participants will be given access to Microsoft Office Web Apps, which include the online editions of Word, Excel, and PowerPoint. The Web Apps are part of Microsoft Office 2010, which rolls out next year.
"While the initial functionality is modest it will expand over time," wrote Office Web Apps program manager Nick Simons, in a blog post Thursday. "As we get closer to the release of Office 2010 we will make the Office Web Apps available to more Windows Live users," said Simons.
"This early peek at the Office Web Apps will include high-fidelity viewing of Word, Excel, and PowerPoint files in the browser. Invitees will also be able to edit Excel and PowerPoint files," Simons added.
Making a version of Office available online allows Microsoft to protect its flank from Web-based software from Google and from free, open source-based offerings, such as IBM's Lotus Symphony product.
Office Web Apps are tailored specifically for the online environment.
For instance, the Office Web version of PowerPoint will not contain the desktop version's high-performance video editing tools. The Web apps, on the other hand, will offer features that won't be found on the desktop versions, such as the ability to embed tags into documents and post them on blogs.
Businesses that purchase volume subscriptions to Office will receive access to the Office Web Apps at no additional charge. Microsoft has about 90 million such customers. It also has roughly 400 million Windows Live users, adding up to a potential installed base of almost a half billion users.
InformationWeek has published an in-depth report on the public cloud, digging into the gritty details of cloud computing services from a dozen vendors. Download the report here (registration required).