Online Spreadsheet System from Google

Spread sheets with difference in all aspects. To write, to maintain, to share and so on.
Yes you heard right! Google is lauching Google Spreadsheets, of course with Ajax stuff to make it as user friendly as possible.
Features:
Creating Spread Sheets
Sharing Spread Sheets
Storing Spread Sheets ...


It can read both CSV and XLS formats.
Files can be saved in CSV, XLS and HTML formats.
Files can be imported in CSV or XLS formats, so excel documents and other spreadsheet files should work in Google Spreadsheets.

Excellent Feature made possible and availble in Google Spreadsheets is - multiple people can update a spreadsheet at the same time and chat with eachother while doing
Before it is made public you can signup and visit the tour.
Some more Ajax based Spreadsheets are available here:
ZohoSheets
iRows
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