Loggingproxy is a project mainly written in Ruby, it's free.
A TCP (or HTTP) proxy with logging features
Usage: loggingproxy [ options ... ] --host name Connect to this computer --port N Connect to this port --listen N Accept connections on this port --base path Base name for log files --nolog Don't write any log files --http Act like an HTTP proxy --verbose Timings etc --help Show this usage message