For those in range of UK, the next UK Polyday will be in Bristol on 20th November.
See:
http://imakeawesome.co.uk/polyday/A one-day event held in Bristol for everyone who knows that happy and honest relationships don't have to be monogamous, Polyday combines a day of discussions and an evening of cabaret and socialising to give you a chance to meet like-minded people, to build our community and to celebrate its diversity.