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.
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.
uIP is probably the smallest implementation of the TCP/IP protocol stack ever written in a high level language; the code footprint is on the order of a few kilobytes and RAM usage is on the order of a few hundred bytes. uIP is intended to be used in embedded systems running low end 8- and 16-bit microcontrollers.
RabbIt is a mutating, caching Web proxy used to speed up surfing over slow links like modems. It does this by removing advertising and background images and scaling down images to low quality JPEGs. RabbIT is written in Java and should be able to run on any platform. It does depend upon an image converter if image scaling is on. The recommended image converter is "convert" from the ImageMagick package.
lb is a very small and efficient libevent-based benchmarking tool for HTTP servers. It has been implemented with the main goal to provide a safe and quick replacement for the Apache 'ab' tool. Since its first release, it comes with the ability to benchmark several HTTP servers at the same time, theoretically limited only by operating system limits.
Kannel is a WAP gateway. It attempts to provide this essential part of the WAP infrastructure freely to everyone so the market potential for WAP services, both from wireless operators and specialized service providers, will be realized as efficiently as possible. It also works as an SMS gateway for GSM networks. Almost all GSM phones can use it to send and receive SMS messages, so this is a way to serve many more clients than just those using a WAP phone. Kannel was among the first WAP gateways to be certified as WAP 1.1 compliant.
Das Schaefchen is a lightweight HTTP server and proxy for Unix platforms. It supports the minimum requirements of the HTTP/1.1 protocol and virtual hosts, basic authentication (which can be used to protect either files or directories), directory listing, byte ranges, reverse proxy, and FastCGI. It is an event-driven server that runs as a single process with a single thread using non-blocking I/O. It uses epoll as the event notification mechanism to multiplex control between active connections.