In Calgary, there is a Pets Calgary as a Yahoo group, and pet posts are NOT permitted on Freecycle here (though some supplies might be). There is a link to Pets Calgary on the Freecycle site.

Maybe if there is a pets group in your area, you can notify your Freecycle moderator and ask them to put the link on there.

If there ISN'T one - well, what do you do in your spare time?
(Yeah, I have tons of it too)