Helma - An Java based application server which is using ECMA-Script as its scripting language. [Open source, BSD style license] - http://www.helma.org/
UserLand Frontier - Frontier is a full featured application server that connects to XML-RPC and SOAP services. It includes an object database, multithreaded runtime, a content management system, and a bundled http server. It costs $899. - http://frontier.userland.com
C Server Pages - An application server that supports building web applications using C++ and templates with dynamics elements embedded. Supports Linux. By T. Gonzalez. - http://cserverpages.20m.com/
WebCollage Syndicator - Enables businesses to syndicate complete, interactive Web applications and services to partner sites, allowing new forms of Web partnerships. By WebCollage, Inc. - http://www.webcollage.com/
NGASI Application Server - Turnkey Next Generation Application Server solution for Web and Wireless Application Hosting and enterprise environments such as ISPs and IT Departments. - http://www.ngasi.com
SQLData Enterprise Server - An web application server that combines web services and database services together. It provides session management, multi-level authentication, data encryption, load distribution and custom logics. By SQLData Systems, Inc. - http://www.sqldata.com/enterprise.htm
WebHub - An application server that is designed for integration with applications developed in Inprise Delphi. By HREF Tools Corp. - http://www.href.com/
WebObjects - Tool for web application development and deployment. Currently available on *nix, WinNT, and Mac OS X. By Apple Computers, Inc. - http://www.apple.com/webobjects/