A NEC holds the rights (and the reference implementation - which includes a "socksifier" that redirects network calls to a SOCKS server) to the protocol, but there are several freeware implementations.
Applications known to support SOCKS:
- FreeCap - a generic wrapper that will allow you to run pretty much any Windows application atop SOCKS (depending on protocol)
- SSH - with the -D option, newer builds support SOCKS 5 and server-side name resolution
- SS5 - simple, neat, SRPMs available for clean compilation under Fedora
- Proxytunnel - not SOCKS, but useful alongside.