Open Docx, Xlsx, Pptx, Ppsx Online
Besides using the free compatibility pack Microsoft provides to open Microsoft Office 2007 files like docx, xlsx and pptx without Microsoft Office 2007, you can also open these files online alternatively.
ThinkFree is one of the online office applications that lets you open docx, xlsx, pptx and ppsx online. Additionally, if you use Firefox browser, ThinkfreeFox is an extension that lets you open these Office 2007 files from any URL. You can also open other other office documents such as doc, dot, rtf, ppt, pot, pps and hwp. However, ThinkfreeFox is an experimental add-on, so you have to login to install it.
Other online office suite that lets you read Microsoft 2007 files online is Zoho Writer. Beside able to view docx, xlsx and pptx online, Zoho Writer also enables you to export document as docx.