I have a long long list of free things I like to do - mostly physical activities and recreation stuff since I can do them year round here in SoCal. Top ones here are: beach volleyball, indoor volleyball (dollar court fee), running, trail running, hiking, road biking, Mt. biking, kayaking, walking, swimming, body surfing, body boarding, surfing, Frisbee, disc golf, skateboarding, baseball, football, soccer, tennis, rollerblading, kite boarding, SUP, snorkeling, climbing, etc.... Some require you to purchase or rent equipment, some don't. I try to do the many things that don't require expensive equipment to buy or rent unless I already have it.
ETA: in my "downtime" between free activities I borrow (for free!) DVDs, books and CDs from my library for entertainment.