I am looking to create a docshare site. Can anyone put in me the right direction?

I'm looking for open source libraries, tutorials, etc.

In terms of basic functionality, what I am looking for is the user to upload documents (in the formats of Excel, PowerPoint, Word, PDF), the site being able to do some basic file manipulation (e.g. strip author information, determine # of pages), and then being able to preview the document in some sort of in-browser player/preview. Here are some examples of the in-browser preview --
* http://www.slideshare.net/dtracy4/gr...rategy-toolkit
* http://www.gazhoo.com/doc/4610/Strategic+Plan+Template+
* http://www.scribd.com/doc/30775316/B...-5-Study-Guide