Google Docs is one of those web application that I personally use a lot. Only 1 downside. You need to be connected to the internet to view and or edit them. MiGhtyDocs solves this problem. It syncs your documents to your iPhone for later offline viewing. This way you can always cary the latest version of your documents with you.

Another nice feature is that the application is totally free. The app has 1 little problem, it can’t handle google presentation files just yet. Maybe a updated version will support this.
iTunes download link