Michael Robertson promised to announce a new ajax-based application each week. This week, he announced ajaxXLS.com. This version of ajaxXLS.com solves this problem:
My son's Little League season started two weeks ago. The helpful "team mom" emailed a team schedule to all the players. Unfortunately, it was an .xls file requiring Microsoft Excel to open the file. This is not unusual. The majority of Microsoft Word, Microsoft Excel and Microsoft PowerPoint users are casual home users who, like the mom in the above scenario, need to simply open a file that's been sent to them and then print it, or maybe make minor edits and pass it along.
Well before ajaxXLS.com, we still have a legal and proper solution - use a microsoft application viewer. These viewers are available for download at Office download center. Alternately, as suggested by Michael, we can also use OpenOffice to open any Microsoft office documents.
One unique feature of the current version of ajaxXLS.com is the ability to "create a link on your website that opens any spreadsheet in ajaxXLS."
Anyway, as Michael said, it is "Halfway to ajax-Excel" and I look forward to seeing the other halfway.