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. It can also be deployed stand-alone by a website administrator to provide spreadsheet editing with a rudimentary CMS.
Expr4J aims to provide a general purpose expression parser, which is also compatible with Microsoft Excel. It will provide an implementation of the built in functions in MS Excel as well as a calculation engine.
JFormulaEngine is a formula engine that runs spreadsheet-style formulas in any context. The function library is fully extensible and the engine can resolve variable names to any context, such as a CMS or spreadsheet, that is supported by JFormulaEngine.