In light of the recent password scare re web based Messenger and mail accounts, change your passwords at your earliest convenience. That is another way of saying ‘NOW’..
Please note that you will have to log into your account with your old password initially..
Yahoo
http://help.yahoo.com/l/us/yahoo/edit/id_password/edit-13.html
MSN
https://account.live.com/changepassworddl.aspx
AIM
http://help.channels.aol.com/kjump.adp?articleId=218553
ICQ
http://www.icq.com/support/security/icqlite/password.html
http://mail.google.com/support/bin/answer.py?hl=en&answer=6567