ProxyChecker - Only software, that downloads free proxy lists from network, and checks them.

Frequently updated list of proxy list URLs;
Fully automated proxy list Descargar and checking;
Supported proxy protocols: SOCKS4, SOCKS4A, SOCKS5, HTTP (HTTPS), WinGate-Telnet;
GeoIP support;
Proxy reply speed checking (ping);
Simplicity in use.