Rspamd is an anti-spam system designed to work faster than SpamAssassin by using the event model and various optimizations. Its most important features include regexp and Lua rules for filtering different parts of messages, a number of built-in functions for analyzing messages, fuzzy hash support, SURBL filters, email and character table support, a control interface for remote managing and stats gathering, a Lua plugin system, statistics support (OSB/Bayes), and an AJAX-based Web interface.
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.
Syncless is an experimental, lightweight, non-blocking (asynchronous) client and server socket network communication library implemented in Stackless Python 2.6. It contains an asynchronous DNS resolver (using dnspython) and an HTTP server capable of serving WSGI applications. It aims to be a coroutine-based alternative of event-driven networking engines (such as Twisted and FriendFeed's Tornado). It is already about that fast, but it has fewer features and is less stable now.
Mr Bix is a TCP proxy of sorts in which an incoming connection becomes two outgoing connections, only one of which returns data to the original incoming connection as with a normal TCP proxy; data returned from the other is discarded. It is intended to be used to permit testing of new services or servers with live traffic.
sec-wall is a feature-packed security proxy that supports SSL/TLS, WS-Security, HTTP Auth Basic/Digest, extensible authentication schemes based on custom HTTP headers and XPath expressions, powerful URL matching/rewriting, and an optional header enrichment. It's a security wall with which you can conveniently fence otherwise defenseless backend servers.
SSLsplit is a tool that performs man-in-the-middle attacks against SSL/TLS encrypted network connections for network forensics and penetration testing. It terminates SSL/TLS and initiates a new connection to the original destination, logging all data transmitted. It supports plain TCP and SSL, HTTP and HTTPS, and IPv4 and IPv6. For SSL and HTTPS, it generates and signs forged X509v3 certificates on-the-fly using the original certificate's subject DN and subjectAltName extension. It supports Server Name Indication, RSA, DSA, and ECDSA keys, and DHE and ECDHE cipher suites. It can also use existing certificates if the private key is available.