Free Museum Day is a list of free museums and musuems with free admission days. This is a great way to save money and get your kids into a variety of cultural activities.
There are usually many different sporting events happening when the weather is nice. Look for special days where there are giveaways or cheaper tickets.
Check out daily deal sites like Groupon and Living Social for deals up to 90% off.
Most cities have a children's museum which has a ton of hands-on activities for the little ones, so they can play and learn at the same time. Look for free or more affordable days on their websites, or buy a membership, so you can go as many times as you like.
Make your own scavenger hunt that either leads around your backyard or your neighborhood. The kids will have fun and use critical thinking skills. Invite their friends over and they can work as a team to solve clues.
Look online for tours of your city, walk your own or look for a free downloadable tour where you can also go at your own pace. Learn more about the history of your city and the buildings and landmarks around town.