Socks Proxy Checker (SPC) can test the details (speed, version, country, smtp, udp and whether gateway or dangerous) of the socks proxy. To have a brand new feeling of checking socks proxy. SPC can also change the socks proxy of your IE and Firefox.
NIX is a proxy checker that supports HTTP(S) CONNECT and SOCKS 4, 4a, and 5. It is multi-threaded and supports country detection, protocol auto-detection, and delay information, and has filters based on IP subnet mask, port, and RDNS.