I only chanced upon this while I was checking my Gmail account.
Apparently, Google Spreadsheets is Writely‘s counterpart for spreadsheets.
It lets you create a new spreadsheet online or upload an existing spreadsheet from your own files.
As a spreadsheet program, I found it familiar and easy to use. Of course, it only has simple functions and it cannot be too familiar because some top spreadsheet company may sue Google for copyright infringement under the “look and feel” doctrine.
Uploading and existing file was simple and straightforward and the fidelity is adequate. Moreover, it saves your work online so you can access and edit it from any computer connected to the internet.
This online functionality likewise allows online collaboration. But I haven’t tried this out yet.
Anyway, it’s still in Google Labs so there will be changes and improvements in the future.
You can check it out here.