I know of several other places.
1) Lenexa Community Center off 95th and Pflumm has open gym (called "Gym for Me") for $1/toddler on Mon. and Wed. from 9-11am most weeks. Sometimes they have an event scheduled in the gym. We've been and think it's great.
Lenexa Community Center: 13420 Oak Street, Lenexa, KS 66215, Phone ###-###-####. "Children ages 5 years and younger, along with a parent, are invited to drop-in for *GYM FOR ME*. This program is designed to provide children a non-structured place to run, ride, and play while exercising, making new friends and having fun. Numerous play items will be available including push toys, riding toys, balls and inflatables. Adult
supervision is required."
2) The Explorer Room in Matt Ross Community Center (new Overland Park community center). It's FREE and open any time the community center is open. It is unsupervised.
"Let your child discover the wonders of the Explorer Room! This three-story "jungle" playground is full of adventure and excitement, which will keep your son or daughter busy for hours. The room has slides and tunnels - perfect for any child who wants to escape into the unknown world of lions, tigers and bears. The Explorer Room is for children, ages 2 to 10."