Ok....here's an outtake of a source file for my iptables script...Yahoo by far takes up the most space......obviously the envars and such will be different but you're most interested in the ports and ip's.....

#
#
# Chat System Blocks
#
# AOL
#$IPT -A SHUN -d 64.12.161.153 -j BAD_IP
#$IPT -A SHUN -d 64.12.161.185 -j BAD_IP
#$IPT -A SHUN -d 64.12.200.89 -j BAD_IP
#$IPT -A SHUN -d 205.188.179.233 -j BAD_IP

# Block Yahoo Messenger
#
# Yahoo Music
#$IPT -t filter -A OUTPUT -p tcp -s 192.168.100.0/24 -d 0/0 --dport 1755 -j $STOP
#
#$IPT -t filter -A OUTPUT -p tcp -s 192.168.100.30/32 -d 0/0 --dport 5050 -j $STOP
#$IPT -t filter -A OUTPUT -p udp -s 192.168.100.30/32 -d 0/0 --dport 5050 -j $STOP

# cbs.yahoo.com
$IPT -A SHUN -d 204.71.202.58 -j BAD_IP

# msg1.edit.vip.sc5.yahoo.com
$IPT -A SHUN -d 216.136.225.238 -j BAD_IP

# dl1.yahoo.com thru dl4.yahoo.com
$IPT -A SHUN -d 204.71.201.134 -j BAD_IP
$IPT -A SHUN -d 204.71.201.141 -j BAD_IP
$IPT -A SHUN -d 204.71.200.36 -j BAD_IP
$IPT -A SHUN -d 204.71.200.37 -j BAD_IP

# p1.msg.yahoo.com thru p5.msg.yahoo.com
# p7.msg.yahoo.com thru p18.msg.yahoo.com
$IPT -A SHUN -d 204.71.202.79 -j BAD_IP
$IPT -A SHUN -d 204.71.202.78 -j BAD_IP
$IPT -A SHUN -d 204.71.202.57 -j BAD_IP
$IPT -A SHUN -d 204.71.202.56 -j BAD_IP
$IPT -A SHUN -d 204.71.202.136 -j BAD_IP
$IPT -A SHUN -d 204.71.202.138 -j BAD_IP
$IPT -A SHUN -d 204.71.202.26 -j BAD_IP
$IPT -A SHUN -d 204.71.200.86 -j BAD_IP
$IPT -A SHUN -d 204.71.200.153 -j BAD_IP
$IPT -A SHUN -d 216.115.105.112 -j BAD_IP
$IPT -A SHUN -d 216.115.105.113 -j BAD_IP
$IPT -A SHUN -d 216.115.105.114 -j BAD_IP
$IPT -A SHUN -d 216.115.105.115 -j BAD_IP
$IPT -A SHUN -d 204.71.202.84 -j BAD_IP
$IPT -A SHUN -d 216.115.107.252 -j BAD_IP
$IPT -A SHUN -d 216.115.107.253 -j BAD_IP
$IPT -A SHUN -d 216.115.107.254 -j BAD_IP

# old cs[1-9].msg.yahoo.com ips...kept just for the heck of it
$IPT -A SHUN -d 204.71.202.119 -j BAD_IP
$IPT -A SHUN -d 204.71.200.55 -j BAD_IP
$IPT -A SHUN -d 216.115.107.146 -j BAD_IP
$IPT -A SHUN -d 204.71.200.57 -j BAD_IP
$IPT -A SHUN -d 204.71.201.100 -j BAD_IP
$IPT -A SHUN -d 204.71.202.59 -j BAD_IP
$IPT -A SHUN -d 204.71.202.58 -j BAD_IP
$IPT -A SHUN -d 204.71.200.54 -j BAD_IP
$IPT -A SHUN -d 216.115.105.57 -j BAD_IP

# Block messenger.yahoo.com
$IPT -A SHUN -d 216.109.116.177 -j BAD_IP
$IPT -A SHUN -d 216.136.232.153 -j BAD_IP
$IPT -A SHUN -d 66.163.172.51 -j BAD_IP
$IPT -A SHUN -d 216.109.116.176 -j BAD_IP

# Block MSN using Squid
# Note: You can try blocking all inbound/outbound to ports 6891:6901 and 1080
# but I don't believe that works anymore.