Microsoft have announced the file formats for Office 2007, the next version of Microsoft Office which is due to be released in early 2007. The most notable change is the obvious visual change in file names. No longer based around 3 characters (e.g. .doc), they are now 4 letters long.
Word = .docx
Excel = .xlsx
Powerpoint = .pptx
The naming change reflects the new xml technology being used by the files. We can but help think it reflects a desperate need to show that things have changed with Office 2007. But we're probably wrong.
The files will allow backwards compatibility with older versions of Office. Office will also support natively a save as PDF feature, and saving files as XPS. XPS is a file format that allows for advanced digital rights. The Office 2007 is still be trialed in beta, which you can get online.
News source: Aviran's Place - see for full list.