CCProxy - Want to share Internet connection? Get every computer online through a single Internet connection?
3proxy - 3proxy freeware proxy server for Windows and Unix. HTTP, SOCKS, FTP, POP3
Apache Traffic Server - Fast, scalable and extensible HTTP/S 2 and 1.1 compliant caching proxy server.
FreeProxy - Feature summary from website:* Internet connection sharing with demand dialling
TinyProxy - A lightweight http(s) proxy daemon
Varnish - High-performance HTTP accelerator