Netstat is probably the most helpful prog in linux.  It allows you to determine the IP's of people who you are connected to.  Therefore, it can be used to determine the IP's of people in many instant messenging progs including ICQ and MSN.  Many of these messenging progs use DCC to your computer (they directly connect in other words).  In ICQ, the entire conversation is DCC'd.  So at any point of the conversation, you can run Netstat (preferably Netstat -n) and your targets IP will be under the list somewhere...  THis is why I recommend you connect to ICQ using anonymous proxies and stuff or your IP is easy to obtain.

In MSN however, the only time a direct connection is established is when a file is being sent.  Anytime else throughout the conversation, trying Netstat will only obtain the IP of the MSN server.  So just send or accept a file and Netstat -N away... Of course the easier alternative would be to get them to email you and extract the IP address from the header, but this text is only about fucking with Netstat. For other shit, look at my social engineering text.