Kind of hard to find absolutely free activities, if you've exhausted museums, parks and outdoorsy things like hiking/biking. But there are lots of stuff to do that only cost a little, like the dollar movies out on east Washington Street. My 16-year-old boy likes to go to Broad Ripple for coffee. You could try something new at an ethnic bakery (Merry's Bakery has a great variety of Hispanic treats and is inexpensive). You could go thrift shopping and see what treasures you can find for $5 at a Goodwill thrift shop. You could browse around Saraga International Grocery and pick out some interesting international food or even candy to try (a visit to Saraga is like a field trip). Stop in for bubble tea (my teenager loved it) at Saigon restaurant, a little Vietnamese place on Lafayette Road. You could go to unusual stores just to look; my kids like to browse around pet shops even if we aren't buying anything; it's just fun to look at animals like ferrets and iguanas that you don't see every day.