HttpdBase4J is an embeddable Java Web server framework that supports HTTP, HTTPS, templated content, and serving content from inside an archive or from the classpath. The classes are easy to extend as they utilize the "don't call us, we'll call you" principle to allow the user to override the framework behavior during all the different phases of the HTTP transaction.
Restlet is a REST framework for Java. It supports all REST concepts (Resource, Representation, Connector, Component, etc.) and is suitable for both client and server Web applications. It supports major Web standards like HTTP, SMTP, XML, JSON, WADL, and Atom. Many extensions are also available to integrate with Servlet, Spring, Jetty, Grizzly, Simple, JAXB, JAX-RS, JiBX, Velocity, or FreeMarker. A GWT version is also available.
Dwarf HTTP Server is a full-featured Web server with a Java Servlet API 2.2 implementation and JSP support. Since it is based on the Dwarf framework, it shares its common design principles: powerful security architecture, modularity and extensibility, XML-based configuration, uniform logging, and remote management.
WebComp is a tool for using scripting to compose and configure Web sites from various existing components, such as static HTML, Java Servlets, Java server pages, and others. It includes a scripting language, a component model/framework, and a set of basic pluggable components to use with it. It is based on Java Servlets.