When you type in Google "Excel Viewer" you see only links to Excel Viewer 2003 but they released a fresh copy 6 March 2008, you can download it here: http://www.microsoft.com/downloads/details.aspx?FamilyID=1cd6acf9-ce06-4e1c-8dcf-f33f669dbc3a&displaylang=en

Helping out MS to be search engine friendly...