Surprised ? I was too. According to the official announcement, Office 2010 for Mobile will be free to download for all Windows Mobile 6.5 based phones with an earlier version of Office Mobile. Though Windows Phone is still due at least 3-4 months, you can have it from Windows Phone Marketplace.
Here are Official Videos of Office 2010 Mobile if you want to know more about it before installing in your Windows Mobile.
And Follow this search result in Bing to see all of them in one place