I was just in Washington DC recently, and while looking up spotting information for KIAD, I stumbled upon the Washington Baltimore Spotters group. (www.washbaltspotters.net)

I was thinking it might be a good idea to start something like that here, in Seattle, as I am new to aviation photography, and it would be awesome to go shooting with others. I would be more than happy to set this up, but I wanted to make sure that A. people were interested, and B. there wasn't something already like this. I know there are a lot of Seattle-area spotters, it would be nice to be part of an organized group.

I don't have a camera but I'll join ya!

I am not in Seattle any longer but 20 years ago there was a huge group spotting, listening to the radios. Now there is a 3rd runway where we used to gather!

I live in Yakima, but I would be up for it a few times a year when I am in Seattle 
I was a part of one in MSP and it was pretty fun!!

There is a fairly large spotter/photographer community in the area already but not formally organized. I haven't been very active the past year or so but when I was I ran into people more often at PAE and BFI - SEA just isn't all that good of an airport to spot at comparatively. The 'water tower' is the only area for a group to really gather and its a bit removed particularly if traffic is on the 3rd runway.

Here is a Flickr group for some of the area photographers if your looking for contacts: http://www.flickr.com/groups/pnwap/