an embeddable spreadsheet for your web application
...Most basic features are implemented as well as some of the more advanced ones. The user interface is written entirely in JavaScript and its server-side API is pure Java based on the OpenXLS spreadsheet engine. Neither the client nor the server needs Excel or any browser plugins.
Sheetster is primarily intended for developers who want to integrate spreadsheets into their web applications. Towards that end it provides a server-side API for document storage connectors and a rich REST API for manipulating open spreadsheets. ...
SameDesk is a common workspace for web applications. Supporting applications written in AJAX, Java, Flash, & Server-generated HTML, it lets applications across domains work together for the users via a familiar window GUI delivered via web browsers.