I'm seeing lots of hits on the 'ole blog from folks looking for some info on this year's Greenfield Planked Salmon Supper.
From what I have scraped online, it looks like it is held on the last Saturday in July. For 2012, that is July 28th.
Hope this info helps!
Here's a video I shot with my old point and shoot (apologies for the quality), showing the salmon cooking in front of the open fire. Yummah!