sSocks is a package which contains: a socks5 server implements RFC 1928 (SOCKS V5) and RFC 1929 (Authentication for SOCKS V5), a reverse socks server and client, a netcat like tool and a socks5 relay.
Antinat is a flexible SOCKS server and client library for writing proxy-based applications. It supports SOCKS 4, SOCKS 5, authentication, CHAP, XML firewalling, Win32, server chaining, and UDP. It also contains very experimental IPv6 support.
MOCKS is a small, easy configurable, RFC1928 compliant SOCKS 5 server for Linux and Linux-like systems. MOCKS supports upstream proxy and IP-based client filtering rules.