Ok since Trillian has been mentioned, its time to mention a wee problem I have had a few times.

Never, ever, try and add a second contact list to it. You will find that the contacts from both are merged, and suddenly your email inbox is FLOODED with people saying "Who in the world are you and WHERE did you get my email address?!?!".

Many got angry. So never, ever, add two msn addies to trillian at the same time. Big boo boo.