Google Docs & Spreadsheets

Create basic documents and spreadsheets from scratch.
You can easily do all the basics, including making bulleted lists, sorting by columns, adding tables, images, comments, formulas, changing fonts and more. And it’s free.
Upload your existing files.
Google Docs & Spreadsheets accepts most popular file formats, including DOC, XLS, ODT, ODS, RTF, CSV, etc. So go ahead and [...]

ZOHO Sheet – Online Spreadsheets

Create and share interactive spreadsheets on the web
Create, edit and access your spreadsheets from anywhere. No installation required.
Share documents with your friends or publish them for public view.
Allow multiple users to work on a spreadsheet simultaneously.
Copy-n-paste from Excel or import an Excel file.You can also export back.
Sync up with remote data from the web or [...]

Web-based spreadsheet viewer – ajaxXLS Viewer

Open any .xls file within your Firefox browser. Compatibility with Microsoft Excel and OpenOffice allows ajaxXLS to preserve all your common cell formatting categories such as text styles, decimals, currencies, dates, and times as well as formulas, backgrounds and borders from the original documents.
The ajaxXLS web-based editor is still in the early stages of development. [...]