App for File store and viewer I am looking at an ipad app which can be used to store files locally as well as supports multiple types for viewing. E.g. Doc, xls, ppt, etc

I heard Goodreader is one such app, but was looking for something free..
What about Documents 2 Free. I use it and I like it.

http://itunes.apple.com/ca/app/documents-2-free-spreadsheet/id314894105?mt=8

Although it's not an ipad only app.