For a spreadsheet in particular, I'm not 100% sure what's out there for doing this (other than the obvious solution of just putting the file on shared drive and emailing or yelling over the cube walls to arrange access). But, in a more general sense, there's a bunch of "stuff" out there that deals with collaborative editing of documents... here are some pointers that might be useful:
You might also consider a wiki... I think there are some wikis that will let you use tables, and then export the resulting data in Excel format. XWiki might have that, can't remember offhand.