EditGrid is an online spreadsheet service with real-time-update and extensive collaboration features.

The differences between EditGrid and desktop spreadsheet applications are real-time update and collaboration. It enables user to manage their spreadsheets through the Internet and lets you to work on your spreadsheets anytime and anywhere.
EditGrid feature:

• Real Time Update (RTU) - allows multiple users to work on the same spreadsheet simultaneously.
• Remote Data Update - Changes of external data will be updated to your spreadsheet every 1 minute.
• Full Keyboard Control - Arrows and hotkeys for power users.
• 500+ functions - SUM(), SUMPRODUCT(), COUNTIF(), VLOOKUP(), …
• Data formats
• Import and Export (Excel, CSV, HTML, Gnumeric, Lotus, OpenOffice…)
• Excellent Permalinks - Permalinks your spreadsheet through easy-to-understand URL.
• Full Access Control - Owner can modify access control settings.
• Cross Browser - supports Internet Explorer 6.0+, Firefox and other Gecko-based Browsers.
• Publish to Blog - publish your spreadsheet online.
• Bookmarklet - allows you to open spreadsheet files from any web page in one click.
• Charting - can generate 36 chart types
• Viewer - a handy tool to view spreadsheet without downloading anything.
• Note and Tag - add note and tag to describe and classify a spreadsheet.
• Freeze Pane - helps to keep column and row label visible while scrolling through the spreadsheet.
• Linked Sheet - allows many spreadsheets to draw and utilise data from a central, master spreadsheet.
• Finder - allows searching of spreadsheets in your own workspace.
• Multilingual
• API - allows EditGrid to be integrated into other applications

EditGrid personal accounts is free, to start using EditGrid, you may sign up for a free personal account at the SignUp page. For more information, visit the Help page.

I personally prefer this product. It’s the best I’ve seen. It is a lot better than Excel at what I use spreadsheets for.