Apple just released the beta version of iWork an addons to your iCloud account. The new iWork will let you create a Powepoint Presentation, Word Documents and Excel Spreadsheets straight from your web browser and can be access in both PC and MAC. So, if someone send you a document in your email you can now open it from your web browser, you can also access these document from your mobile apps keynotes, number and pages.
Below is the screenshot of iWork creating a Word Document in my firefox web browser that looks like an mobile apps.
The beta released is available for Developers Account and can be access on https://beta.icloud.com.
To read more about iWork check the Official page at http://www.apple.com/iwork/compatibility/