See a movie
At night when the temperature (hopefully) drops down to a reasonable number, there are all those fabulous free alfresco films. But when the sun's up, there's no reason to pay full price to cool off at an air-conditioned flick. Clearview Cinemas, which has locations in Chelsea and the Upper East Side, runs a Summer Kids' Club featuring screenings of last year's hits (How to Train Your Dragon, Shrek 4, Megamind and Despicable Me to name a few) on Wednesday and Thursday mornings at 10:30am for free. Runs July 6-August 25. Click here for the complete schedule.

Hang at a mall
No, we're not suggesting you go to the 'burbs. There are plenty of upscale indoor shopping centers right here in NYC, many of which offer activities for kids. The Borders at the Time Warner Center has a free children's storytime every Saturday morning at 11am. Afterward, watch short videos about jazz greats at the Ertegun Jazz Hall of Fame. Queens' Shops at the Sky View Center hosts complimentary concerts. And Grand Central Terminal's got trains (we hear some kids enjoy those), eclectic stores and eateries, and The Transit Museum Store and Gallery Annex.

Meet the Muppets
The Smithsonian traveling exhibition, Jim Henson's Fantastic World, which opens July 16 at the Museum of the Moving Image, explores the creative process and singular career of the world famous puppeteer, filmmaker and television pioneer. Highlights include 15 iconic puppets (Miss Piggy, Kermit, Bert, Ernie and more), video material, sketches and drawings, and more than 100 artifacts relating to Henson's films, television shows, and other creative projects. Alongside the exhibition, the Museum will present family matinee screenings every weekend at 1pm of Muppet movies and special compilation programs. Special family workshops will also be offered. Visit the website for more information.

Explore more museums
We recently visited the Transit Museum in Brooklyn Heights and just loved it. There are also the children's museums: the Brooklyn Children's Museum; the Staten Island Children's Museum, which is located on the stunning Snug Harbor grounds; the Children's Museum of Manhattan, which has a great Curious George exhibit on view; and the Children's Museum of the Arts, which has all kinds of creative hands-on activities. And there's always the American Museum of Natural History, which currently has two great special exhibits, The World's Largest Dinosaurs and Frogs: A Chorus of Colors, the always free Sony Wonder Technology Lab or all of the kid-friendly exhibitions at the "grown-up" institutions. Click here for all of our museum posts.

Hit a play space
There are a ton of drop-in indoor play spaces to choose from in this town, and new ones seem to open all the time (especially in Brooklyn). Most are aimed at children under 6, but some accommodate older tykes. We recently visited Play and The Gym Park, which are both in Greenpoint, and Klub 4 Kidz in Williamsburg. But we like plenty of veteran spots, too, like Chelsea's City Tree House, where kids can play in (what else?) a tree house and splash around at the water table, or LIC Kids in Long Island City. Be sure to call ahead to verify each spot's open play hours, especially in the summer when many of them run camps.

Play at a store
My kids and I recently spent a 100-degree afternoon in the icy land of Red Hook's Ikea. For a couple of bucks, we ate in the cafeteria, and then let the kids clang together cute wooden toys in the Småland Play Area, which offers free childcare for up to an hour while you shop. There's a section in the store where wee ones can play Goldilocks on all the miniature beds, try out slides, rocking horses and climbing tunnels, and pick an 89-cent toy to bring home. Other amusement filled the Disney Store in Times Square, which, even though it opened last November, has already undergone a makeover. All of these spots are free—assuming you can leave without buying anything. Click here for additional stores where kids can play.

Go to the library
Have you signed your kid up for Summer Reading 2011 yet? There's still time as summer has literally just started. Hit your local branch to pick up books that are (or aren't) on the list, and see what kinds of activities and entertainment are scheduled for the season. The Children's Center at 42nd Street regularly hosts fantastic free programming for families, from simple storytimes to shows and concerts. The central branch of the Brooklyn Public Library also features wonderful family activities. But so do lots of local branches. Some friends of mine just saw Gustafer Yellowgold play a free show up at the Mott Haven library. In light of the terrible budget cuts our libraries are facing, consider making a donation to help keep these free (and cool) havens operating.

Visit an indoor public space
When we originally wrote about these 16 indoor public spots, it was the dead of winter, so we were all about staying warm. Now you can duck into these atriums and plazas to cool off. Many host art displays, and at the Winter Garden at the World Financial Center you'll often find entertainment. But sometimes you don't need amusement—just a place to sit and relax in air-conditioning.

For more indoor play ideas, see our Inside Activity Guide.