A very Bouldery place to be and be seen. One of the biggest and busiest farmer's markets I've seen in Colorado. Organics galore and plenty of free samples. Pricey, but hey, it's Boulder.
This is a truly great Boulder tradition. I go every Saturday with my kids, get some dumplings from Sister's Pantry, they do an art project, I get some fresh veggies, teas, meats for the weekend BBQ.
Go to the Boulder Farmers Market. Try the Noosa yogurt and spend a lazy afternoon in the grass nearby. There's sure to be some activity to watch or join in on.