Don't underestimate the potlucks! I know you don't want food ideas, but that is one that has been really successful with our meet-up group here in Seattle.
Other ideas we've discussed:
-Berry picking (gathering)
-Visiting a local farm
-Camping (we're really looking forward to this one)
-Paleo Thanksgiving (food, yes, but we did do this and it was great)
-Cooking lessons & techniques
-We're also doing an event this month at Whole Foods with Robb Wolf, a Paleo Cook off, where 3 local chefs compete to make the best meal using only Paleo ingredients, plus a talk by Robb Wolf. It was VERY popular and sold out quickly.