In Computational Geometry, over half of Dr. Pless' office hours are only held over AOL Instant Messenger, and 80% of the TA office hours are done the same way. This includes the weekends.
It's a perfect excuse, and my parents had little choice but to concede the point. Instant messaging services are no longer contraband- my father decided there's nothing I can do but accept the system security risk, and he overruled my mother's fear about "those perverts on the Internet", observing that, just maybe, I'm intelligent and mature enough to deal with it. (Of course, as many of you are aware from previous writing endeavors of mine I've linked to, I am one of those perverts on the Internet.) It only took them a year and a half of me being at college to decide that I might have developed enough maturity to talk to people online.
So I may or may not be on during the weekends. I'm not going to push my luck- the nonzero size of my AIM contact list is implausible at the moment- but it's another point in my favor.