Sun Java System Application Server
- Documentation, support, and downloads.
- http://developers.sun.com/appserver/

Borland Enterprise Server AppServer Edition
- J2EE application server built on top of Borland VisiBroker. [Commercial]
- http://www.borland.com/us/products/appserver/

Essen Software
- Provides an Enterprise Java Application Server (EJAS).
- http://www.essencomp.com/

JOnAS (Java Open Application Server)
- Open source EJB container from ObjectWeb. Includes mailing list, forums, documentation, download and source. [Open source, LGPL license]
- http://wiki.jonas.objectweb.org/xwiki/bin/view/Main/WebHome

OpenEJB
- EJB container, pluggable into commercial middleware servers. [Open Source]
- http://incubator.apache.org/openejb/

JRun
- Servlet engine that allows the development and deployment of Java Servlets and JavaServer Pages. [Commercial]
- http://www.adobe.com/products/jrun/

Oracle Application Server
- It provides an architecture for developing and deploying business and commerce applications. By Oracle Corporation.
- http://www.oracle.com/appserver/

Accendia Iris Application Server
- Offers synchronous, asynchronous and client callback communication models as well as integrated application security and communication security. [Free for developers and for personal use]
- http://www.accendia.com

Puakma Tornado Server
- A Java application server and framework for complex web application development.
- http://www.puakma.net/

Laszlo Systems Inc.
- Has developed an XML-native platform for deploying rich Internet applications into any browser.
- http://www.laszlosystems.com/

Pramati
- Provides J2EE server and IDE.
- http://www.pramati.com/

Trifork Enterprise Application Server
- A Java 2 Enterprise Edition (J2EE) application server.
- http://www.trifork.com/

Orion Application Server
- A pure java full-featured application-server that supports J2EE and EJB 1.1 [Commercial]
- http://www.orionserver.com/

Enhydra
- Application server with XML features. [Open Source, BSD-like]
- http://www.enhydra.org/