Do you want 1) External IP 2) Internal IP
External IP
Simply go to http//www.whatismyip.com, and there's your IP address as you seen on the net
Internal IP
I DON'T KNOW HOW TO DO THIS ON A MAC but...
If your router is actings as a DHCP server, and you only have one computer attached to it, the likelyhood of the Internal IP being 192.168.0.2 is very very high, unless you have changed your DHCP range
objectifier comments
what objectifier means by your IP changing is whether you get you IP address dynamically from you ISP or whether you have a statis IP. Most ISP will allow you to have a static IP if you ask them.
The question, why do you want your friends?