Today (15, Jun 2010) Microsoft announced that Office 2010 is available in retail, though Volume Licensing customers have been able to get their hands on it since April 27.
In this new version of Office Microsoft main goal has been to make it easier to store, edit and work with files online. With Microsoft Office Web Apps it is possible to keep versions of the same document synchronized so a group of people can work on the same project files simultaneously.
A free beta version is released on:
http://office.microsoft.com/en-us/products/office-products-FX101825692.aspx