Jaxer is a new kind of Web server optimized for Ajax pages and applications. It's open source and 100% free. Use Jaxer's server-side JavaScript APIs to interact with databases and object stores, communicate over networks (FTP, SMTP, HTTP, etc...), interact with file systems, manage state with user sessions, and lots more. Plus since Jaxer runs JavaScript, you can use the same client-side JavaScript language and Ajax libraries you already know on the server too. Use server-side scripts to modify the DOM or create new DOM elements on the server before it goes on to the browser.

Write your client-side and server-side code in a single HTML page. Choose where functions run by adding a simple "runat" attribute. Run functions on the browser, on the server, or even in both locations. You can even remotely call server-side functions from the client without all the mess of the underlying Ajax plumbing -- all of the synchronous, asynchronous, remoting and data marshaling is handled automatically. Imagine writing form validations once that work both at the client and on the server! Jaxer unifies Ajax development and lets you build richer web applications more quickly.

Homepage: http://www.aptana.com/
Download:
Jaxer for Windows (build 0.9.7.2472)
Download the Jaxer Package with self-contained Apache (.zip)

Jaxer for Mac OS X (build 0.9.7.2472)
Download the Jaxer Package with self-contained Apache (.dmg)

Jaxer for Linux (build 0.9.7.2472)
Download the latest update for your current Jaxer (.zip)