Google Docs Viewer supports 12 more file formats

Mirosoft Excel	.xls and .xlsx
Microsoft Powerpoint 2007/2010	.pptx
Apple Pages	.pages
Adobe Illustrator	.ai
Adobe Photoshop	.psd
Autodesk Auto Cad	.dxf
Scalable Vector Graphics	.svg
Postscript	.eps .ps
TrueType	.ttf
XML Paper Specification	.xps