lighttpd is a secure, fast, compliant, and very flexible Web server which has been optimized for high-performance environments. It has a very low memory footprint compared to other Web servers, and it takes care of CPU load. It has an advanced feature set that includes FastCGI (load balanced), CGI, Auth, Output-Compression, URL-Rewriting, SSL, and much more.
The CyaSSL embedded SSL library is a lightweight SSL library written in ANSI C and targeted for embedded and RTOS environments, primarily because of its small size, speed, and feature set. It is commonly used in standard operating environments and cloud services as well because of its royalty-free pricing and excellent cross platform support. CyaSSL supports industry standards up to the current TLS 1.2 and DTLS 1.2 levels, is up to 20 times smaller than OpenSSL, and offers progressive ciphers such as HC-128, RABBIT, and NTRU.
Monkey HTTP Daemon is a very fast and lightweight Web server for Linux. It uses a hybrid networking model based on asynchronous calls (event-driven) and fixed threads, which makes it scalable and capable of attending thousands of clients per second. It provides a powerful API for C and is ideal for embedded devices, thanks to its small core and plugin architecture.
Pound is a reverse HTTP proxy, load balancer, and SSL wrapper. It proxies client HTTPS requests to HTTP backend servers, distributes the requests among several servers while keeping sessions, supports HTTP/1.1 requests even if the backend server(s) are HTTP/1.0, and sanitizes requests.
PasTmon (Passive Application Response Time Monitor) passively monitors your application servers, measuring and reporting user response times, throughput and congestion. It currently works with HTTP, telnet, rlogin, rsh, FTP (control channel), SMTP, POP3, and IRC. Measurements are recorded in a PostgreSQL database and are presented graphically via a PHP Web front-end using R statistical analysis scripts to create the plots.
The goal of the Apache Tomcat Project is to provide commercial-quality server solutions based on the Java Platform that are developed in an open and cooperative fashion. Tomcat 3.x is an implementation of the Java Servlet 2.2 and JavaServer Pages 1.1 Specifications. Tomcat 4.x is an implementation of the Java Servlet 2.3 and JavaServer Pages 1.2 Specifications, and is a re-implementation of the Tomcat servlet engine from the ground up. The current branch, Tomcat 5.x, is an implementation of the Java Servlet 2.4 and JavaServer Pages 2.0 specifications, with increased attention to scalability, reliability, and management functionality.
Unicorn is a Unix and LAN/localhost-optimized fork of the Mongrel HTTP server. It takes full advantage of functionality exclusive to Unix-like operating systems. It will reap and restart workers that die from broken apps, and there is no need to manage multiple processes yourself. Load balancing is done entirely by the operating system kernel. Requests never pile up behind a busy worker. The server does not care if your application is thread-safe or not, as workers all run within their own isolated address space and only serve one client at a time. All Rack applications are supported along with pre-Rack versions of Ruby on Rails via a Rack wrapper. It also supports atomic log cycling, nginx-style binary re-execution without losing connections, before_fork and after_fork hooks, and optional copy-on-write-friendly memory management.