Official Google Docs Blog: View online files using the Google Docs Viewer
Starting today, we're opening up this technology to all webmasters and blog owners with the Google Docs viewer. All you have to do is give the URL of a PDF, Powerpoint or TIFF document to us and we'll display it directly in your browser with no download required - like this. For complete documentation, and a form to generate code for embedded viewers (example below), check out our webpage.
This is a great tool, thanks Google. Since now it's always a problem that few visitor can't read your PDF files because they are missing the Adobe Reader or the installed version doesn't work. I remember me also some travel document attachment my mom tried to open in Outlook express, some Microsoft trouble has disabled that attachment. With this great tool those problems belong to the past.