The Experimental Gameplay Workshop
From the site:
The Experimental Gameplay Workshop is a forum for the demonstration and discussion of innovative game designs. It provides a place for designers to showcase challenging, unproven work, and discuss it with peers.
By explicitly acknowledging the existence of a community of experimental game designers, the workshop helps legitimize gameplay-oriented research and development.
A related festival is The Independent Games Festival at http://www.igf.com/
Thanks Josh