The Free Software Foundation (FSF) runs a website to organize meetings related to free software/open source. It's a wiki so anyone can update it.
I'm using it to organize the Toronto Free Software Group/LibrePlanet Ontario meetups. If anyone's interested in free software and lives in Toronto or across Ontario, we'd be happy to have you subscribe to the mailing list!
For more info: http://libreplanet.org/wiki/Group:LibrePlanet_Ontario
For libreplanet ontario/toronto free software mailing list: http://lists.libreplanet.org/mailman/listinfo/libreplanet-ca-on