This morning Marc seems very happy with His new Yahoo Messenger :) welcome to the club! On His first day of using YM He already found something fun with YM: You can chat with Your self! how to do it? just add Your own Yahoo ID as a new contact. You will need to do some approval for Your self :) after that You can start chatting Your self :p
I try to do the same thing with MSN Messenger but it seems that MSN is sucks :D You can add Your self to Your contact list but every time You double click Your self You will open a new email – in My case I redirected to My Hotmail account with My own Hotmail email address already filled in on the To: field.