Today I came across (thanks to Jason Jones) a new suite of online tools for online collaboration. Zoho provides the three big tools that Google Docs does: word processing, spreadsheets, and presentations (aka PowerPoint). However, it has a larger suite of tools including databases, online conferencing, note taking, and wikis. It also offers email clients, chat, and more. In some ways, though, Google is offering--or will be offering soon--many of these same tools, they just aren't necessarily part of Google Docs.
One thing that I like about Zoho is that it should play nicely with MS Office. There's a plug-in that allows you to work offline and keep your documents in Zoho up to date with the changes you make on your desktop. Something else is that Zoho's editing features within, say, documents are more robust and advanced than Google's.
So if you want a little bit more functionality and interoperability than Zoho might be a good solution.