With
http://viewer.zoho.com/ you can view documents (.pdf, .doc, .docx, .rtf, .odt, .sxw), spreadsheets (.xls, .xlsx, .csv, .ods, .sxc) and presentations (.ppt, .pptx, .pps, .odp, .sxi) online without leaving your browser. Right click link and select "Open in Zoho Viewer".
It's a nice alternative to google docs ;-).