Proxyleech.com - Checked list of proxy servers with IP and port, country, link to whois. List also available in plain text or as an XML file. - http://www.proxyleech.com/
Digital Cyber Soft - List of anonymous proxies. - http://www.digitalcybersoft.com/ProxyList/
Proxy Blind - Information about using proxy servers for privacy, with socks and proxy lists. - http://www.proxyblind.org/
ProxyLists.Net - Free HTTP and Socks proxy lists - http://www.proxylists.net/
OpenProxies - Open, public HTTP proxies, updated daily. - http://www.openproxies.com/