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.
ashttpd was originally a testbed for a kernel async-sendfile patch. Today, it's just another Web server for serving static content rapidly. It differs from its competitors by storing its webroot in a database, which provides a 50% performance increase over using the operating system's VFS. It also allows precalculation of strong cache-validators (ETags).
Higgs.IO is a high performance, message oriented network library built for realtime systems. It provides a core extensible framework and libraries built on top of the core. Libraries include a WebSocket server, an HTTP server and client, and Boson, a custom serialization and RMI library.
NXWEB is ultra-fast and super-lightweight web server for applications written in C. It can serve thousands of concurrent requests with a small memory footprint using an event-driven and multi-threaded model that is designed to scale. It features an exceptionally light code base, a simple API, decent HTTP protocol handling, keep-alive connections, SSL support (via GNUTLS), HTTP proxy (with keep-alive connection pooling), non-blocking sendfile support (with configurable small file memory cache), cacheable gzip content encoding, cacheable image thumbnails with watermarks (via ImageMagick), a modular design for developers, and the ability to run as a daemon.
Alaya is a primitive chrooting Web server with basic WebDAV support. It can serve HTTPS and HTTP, and can authenticate using PAM, /etc/shadow, /etc/passwd, or using its own authentication files that allow for 'native' users that only have access to alaya content. It's intended to be a simple method of sharing content over WebDAV, and though it can be configured with a config file, it's easy to configure by command-line switches alone. Alaya always chroots to ensure that malicious users can't use '..' within a URL to access unintended documents, and that users can't accidentally leave documents in places outside of the chroot. It has a 'ChHome' mode that chroots users into their home directory and serves content from there. It supports .cgi scripts out of a trusted path (so not from within the chrooted WebDAV share) and read-only shared directories that are outside of the chroot (allowing access to shared content when in ChHome mode).