Office 2007 & MOSS 2007

Office Outlook 2007 provides bidirectional offline synchronization with SharePoint document libraries, discussion groups, contacts, calendars, and tasks.
Microsoft Office Groove 2007, included as part of Microsoft Office Enterprise 2007, will enable bidirectional offline synchronization with SharePoint document libraries.
Features such as the document panel and the ability to publish to Excel Services will only be enabled when using Microsoft Office Professional Plus 2007or Office Enterprise 2007.
Excel Services will only work with documents saved in the new Office Excel 2007 file format (XLSX).