Enhydra
Application server with XML features. [Open Source, BSD-like]

Resin
Java based XSL focused on dynamic server pages. This Java servlet engine supports JavaScript and JavaServer Pages (JSP). It also compiles JavaScript templates into Java byte code. [Commercial]

Orion Application Server
A pure java full-featured application-server that supports J2EE and EJB 1.1 [Commercial]

Trifork Enterprise Application Server
A Java 2 Enterprise Edition (J2EE) application server.

JOnAS (Java Open Application Server)
Open source EJB container from ObjectWeb. Includes mailing list, forums, documentation, download and source. [Open source, LGPL license]

Blazix Java Application Server
An app server with support for EJB, JSP and servlets. Includes EJB Wizards, JSP library, and JSP debugging support.

Java Skyline - Servers
Comprehensive list of Java enterprise servers - which ones run JSP, servlet, EJB and who makes them.

Pramati
Provides J2EE server and IDE.

Cape Connect
Web services platform that supports J2EE, SOAP, WDSL and UDDI. [Commercial]

GNU-Paperclips
Servlet API 2.1 servlet container. It provides HTTP/1.1 compliance and has an easy to use admin interface. [Open Source, GPL]

OpenEJB
EJB container, pluggable into commercial middleware servers. [Open Source]

Borland Enterprise Server AppServer Edition
J2EE application server built on top of Borland VisiBroker. [Commercial]

JRun
Servlet engine that allows the development and deployment of Java Servlets and JavaServer Pages. [Commercial]

Jetty
HTTP Server with Servlet support, written in 100% Java. [Open Source]

Sun Java Embedded Server
Dynamic, real-time, life-cycle control for the creation, deployment and installation of applications and services. [Commercial]

Webkool
Includes source, documentation, downloads, and mailing list. [Open Source, LGPL]

JEAS
A Java embedded application server, following OSGi specification. By Coternet Technology. [Shareware]

s-integrator
A "light-weight", adaptable integration server that rapidly integrates services from various systems.

Helma Object Publisher
An Java based application server which is using ECMA-Script as its scripting language. [Open source, BSD style license]

Gefion LiteWebServer
Small, easy-to-use Java web server and servlet runner, based on Apache Tomcat. [Open Source, BSD-like]

WISE Server
A total web infrastructure product. Allows the hosting on multiple j2EE on a single machine. WISE is designed for large intranets or demanding internet sites. By SMart Frameworks Limited.

Laszlo Systems Inc.
Has developed an XML-native platform for deploying rich Internet applications into any browser.

SymTier
A J2SE RMI Application Server for Java Technology providing an API and framework for creating scalable nTier solutions. [Commercial]

Puakma Tornado Server
A Java application server and framework for complex web application development.

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]