Office File Viewer For Website? need some suggestion for online viewer for MS office files.

Hey folks....I m making a website which will be having an uploader for MS office compatible files like doc, ppt, xls n even txt and pdf. Can you please suggest me how to make a viewer for such type of files.... Examples of such type of website is slideshare, scribd.com etc.... but i cant use the dll provided by these websites due to some security reasons for uploaded contents....Can u plz suggest me any way of doing this... I don't know flash coding.. so if any such open source code is available on net or any other better option???Waiting for your replies....Akshit