One of the coolest things in SharePoint ever to happen is the Integration of Office Web Apps right into SharePoint 2010!
You can now view/edit Office documents in the browser itself from SharePoint.
Here is a document library with some docs:
Clicking on the FY10 Sales Plan is going to take me to the Office Word Web App than asking me to open in Microsoft Word
And I can also edit right away!
And then save back the changes
Here is the PowerPoint Web Apps in SharePoint
One small catch – You can’t create new documents using the Office Web Apps.