for blocking social site with below setting
blockfiles urlpath_regex -i "/etc/squid/blocks.files.acl
badsites dstdomain "/etc/squid/badsites
badwords url_regex -i "/etc/squid/badwords""
##should be above of of acl before allow
http_access deny badwords
http_access deny blockfiles
http_access deny badsites
######EXAMPLE BELOW #######
acl CONNECT method CONNECT
http_reply_access deny flash
http_access deny badwords
http_access deny blockfiles
http_access deny badsites
http_access allow internet
http_access allow manager localhost
http_access deny manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
for blocking torrent download can try through delay pool & iptables
http://linuxgazette.net/108/odonovan.html
http://www.squid-cache.org/Doc/config/delay_parameters/