My usage of Facebook has dropped. At the same time, people messaging me / contacting me through there has increased. At least the message shows in email now.
What I am still using quite a bit is the SMS integration for status messages. I know that updating my status sends out SMS notifications to a bunch of my friends, and vice versa. Yes, this is not new -- it's microblogging / Twitter / Jaiku, etc.
The mobile integration grounds the social in the "real world". There is an element of serendipity in sending a ping out to the world, and wondering who might respond back, who else is wandering the streets, cellphone in hand, ready to go for a drink or join an activity.
I imagine when Jaiku gets their US / Canadian mobile integration up and running, I'll use that more.
What SMS services are you using in Canada? Travis' description of SpinVox sounds great -- except for the whole Rogers is the devil and expense of it :P