No, there isn’t one yet, as far as I know, but the latest Web 2.0 thingy really makes the point - why not?

Num Sum allows you to create and share basic spreadsheet applications. And that’s fine, as far as it goes. But since so many people use Excel for what are often common purposes, you’d think that someone would have created a wiki by now where spreadsheet templates could live free in the wild, but more importantly where they could be uploaded, improved by the community and downloaded for everyone’s use.