Microsoft Education Labs has released a Moodle add-in.
The Office Add-in for Moodle (OAM) is an add-in for Microsoft Office (versions 2003 and 2007) that allows teachers to open and save Word, Excel, and PowerPoint documents to a Moodle website.
Future versions will also allow students to save directly to Moodle from Microsoft Office products, and hopefully, a Mac version will follow (Thanks, Dwight).