Glassfish!

JBoss is Red Hats Java EE 5-compliant (soon Java EE 6-compliant) application server. It is, as with Red Hat itself, dual-licensed either as open source (community edition) or commercially (enterprise edition).

appserver.io is a multithreaded application server for php written in php. Our technology allows real multi-threading in PHP and different useful services for developers enabling more efficiency and security. And best of all – it is completely open source!

WebSphere Application Server provides the availability and security your business depends on while optimizing cost.

JOnAS is a leading edge Java EE 5 certified Open Source OSGi Enterprise Server by OW2. The License used by JOnAS is the LGPL. The OW2 development community includes many academic institutes (Grenoble University, INRIA, LIFL, Peking University, UPM, ...) working with JOnAS; this fastens technology transfers and make JOnAS a top level product in term of technology innovation. JOnAS 5 is designed with an OSGiTM based services architecture to provide a dynamically adaptable application server. JOnAS implements the full Java EE 5 execution stack and provides, with EasyBeans, an efficient, pluggable and easy to use EJB3 container. »

The Mako Server is an application server with an API that loosely resembles the Java Servlet API, but where server side web applications are designed in the Lua scripting language. The Mako Server is capable of delivering dynamically generated content faster than Apache can deliver static content.

A Java EE 5-certified application server for web and enterprise applications based on Suns Java EE platform specification. The goal of the Geronimo project is to produce a server runtime framework that pulls together the best Open Source alternatives to create runtimes that meet the needs of developers and system administrators.