Kids, dogs, water and winter, in one place.
Kids
The playgrounds are everywhere: 515 of them in the city, and the Chicago Plays! program rebuilt more than 300 with a goal of a good one within a ten-minute walk of every child, which the city now essentially meets. The best of the best: Maggie Daley's play garden and climbing walls, the Crown Fountain (bring a towel), Oz Park, Indian Boundary's castle when it reopens, Riis Park's new water park, Humboldt Park's beach, and the roughly 200 free spray features that switch on in late June. Free zoo, free conservatories, free nature centers in every county. The living-history farms (Wagner, Kline Creek, Volkening, Blackberry) are the rainy-day and shoulder-season answer.
Dogs
In the city dogs may be off leash only inside one of the 33 Dog Friendly Areas, and every dog needs an annual DFA permit tag, sold through participating vets with proof of vaccinations. Elsewhere it is a six-foot leash, and no dogs on beaches except the two dog beaches, Montrose and Belmont Harbor. Popular DFAs: Wiggly Field, Puptown at Margate, Grant Bark Park, Hamlin, Horner, Portage, River Park, Wicker Park, Walsh and Churchill along the 606, Fred Anderson in the South Loop, Calumet Park. The counties each run permit-based off-leash areas: three in Cook (Beck Lake, Bremen Grove, Miller Meadow), seven in DuPage, five in Lake, six in Will, five in Kane (Kane's need no permit). Suburban dog beaches at Gillson and Evanston are pass-only. Some nature preserves (Ryerson, the Grove, West Ridge Nature Park, Spring Valley) allow no dogs at all.
Water
The 27 lakefront beaches are free with lifeguards 11 to 7 from the Friday before Memorial Day to Labor Day, and swimming anywhere else on the lakefront is prohibited. Open swim at the city's 50 outdoor pools and 27 indoor pools is free; only lap swim needs a membership. Humboldt Park's lagoon beach is free too. Suburban beaches and pools charge, usually less for residents: Gillson, Evanston, Rosewood, Centennial Beach in Naperville, and the big water parks in Bolingbrook, Woodridge, Aurora and Palatine. Grilling on beaches and in parks only in designated spots, coals in the red bins, no alcohol on any Park District land, including beaches, without a permit.
Winter
Sledding in the city: Cricket Hill at Montrose, Soldier Field's snow-making hill, Palmisano's Mount Bridgeport, Warren Park, Humboldt Park, Gompers, Horner and Oz for the little ones. County hills with lights: Dan Ryan Woods (the only snowboarding hill), Caldwell Woods, Westchester Woods and Swallow Cliff, open with three inches of snow. Suburbs: Old School and Lakewood in Lake County, Goodenow Grove's hill with tube rentals, Phillips Park in Aurora, and Mount Hoy at Blackwell for tubing only. Skating: the free Millennium Park rink (bring skates, reserve), the Maggie Daley ribbon (fee), and five free neighborhood rinks including Midway, Warren, McKinley, Mt. Greenwood and Wentworth, roughly Thanksgiving to mid-February. Cross-country skiing at Sagawau, Ryerson, Pilcher Park (rentals) and most preserves with enough snow.