Hm. A Google Docs version is definitely possible, but the fact that it can be edited by more than one person could cause problems if one person messes up any of the formulae on the original document.
For now, OpenOffice (freeware that is readily accessible) should be able to open a simple old-version Excel file like this one.
In the next few days, I'll be working on a more streamlined version for Google Docs, as well as playing around with the coding to revamp some of the features on the Excel document.
There are a few ways to handle this.
1 - make the sheet publicly editable, but lock a "template" sheet. People can copy it and edit the copied sheet. A sort of example of this is the Colosseum Betting spreadsheet.
Pro: Easiest for people to use, doesn't require downloading a file or making a google duplicate.
Con: The main template is safe, but visitors can vandalize each other's stuff.
2 - make the sheet viewable but not editable. People can download it in Excel or OO format, or make a google docs copy. An example of this method is my MatrimBot spreadsheet.
Pro: The template and user's sheets are safe from trolls.
Con: People have to put forth the "effort" of saving a copy. You'd be surprised how much of a damper this simple step has on usage rates.
Either way, when you do your editing, streamlining stuff, Docs is the most limited of the 3 formats, so if you get it working on Docs, you can safely export it to any other spreadsheet software.