NanoHttpd is a lightweight HTTP server designed for embedding in other applications. It's only one Java file, in two "flavors", one strictly Java 1.1 compatible, and one at "current" standards. It supports GET, POST, PUT, HEAD and DELETE requests, and supports file uploading with very small memory overhead. Temp file usage and the threading model are easily customized.
Fulworx is a REST framework that uses simple annotations of XWork "Action" implementations to expose restful interfaces. Similar to Struts, Fulworx sits as a controller on top of Restlet. Each action is attached as a resource using Restlets. Standard resources are represented by default as XML (or JSON) using JAXB, but any representation may be specified. Actions may be used in other frameworks such as Struts and Webwork, since they're just XWork implementations.
PSX is a PHP framework for creating RESTful APIs. It helps you to build clean URLs serving Web standard formats like JSON, XML, Atom, and RSS. It includes a handler system that abstracts away SQL queries from domain logic, a routing system that executes correct controller method for the location of the controller and the method annotation, and a flexible data system that converts database records into formats like JSON, XML, Atom, and RSS. A lightweight DI container handles dependencies. The controller supports request and response filters that can modify the HTTP request or response, and filters are provided for Basic and Oauth authentication.