Free US Socks 5 Proxy List

SOCKS is an Internet protocol that routes network packets between a client and server through a proxy server. SOCKS5 additionally provides authentication so only authorized users may access a server. Practically, a SOCKS server will proxy TCP connections to an arbitrary IP address as well as providing a means for UDP packets to be forwarded. More at Wikipedia

Those proxies above probably not too much, but i think 3 seconds timeout and refresh every one hour is more than enough to do, but if you really need more, stay tune at Servers Review