Docufarm is a Firefox extension that lets you preview online documents. Everytime you click on a link to a PDF, PostScript file, Word document or PowerPoint presentation, the file is quickly downloaded on Docufarm's servers and you can see an almost instant preview of the file. Unlike what you see from Google's cache, Docufarm preserves the original formatting of the document and shows the images included in the document. While the file is searchable, the Docufarm interface only shows images for each page of the document, so you can't copy text.
This extension is useful for a quick overview of a document because the interface doesn't make reading the document an easy job (except for the PowerPoint presentations that look very nice in the slide view).
Docufarm also lets you search for supported documents available online and the results seem to be provided by Google.
{ Thank you, Laurent. }