More to explore:
I could just about do this with stuff hired from the toy library and ball pit balls...
pool noodle bath pit
DIY Homemade ball pit made with PVC pipes!
Home made ball pit for kids. Use PVC from Home Depot and balls from toys r us
Homemade ball pit under $100 without the balls, and under 2 hours to make
DIY Homemade ball pit made with PVC pipes! Looks like I found a kid's playroom project for dad to make the boys!
Best Birthday Presents for One-Year-Olds: a DIY Ball Pit!
Ball Hoops made from pool noodles - use them in the bath, on back of doors, on walls around the house, outside, anywhere! Great for basketball and other fun ball games ( like color sort noodle toss )
Disney Mickey Having-a-Ball Inflatable Ball Pit...bday ideas
Playroom Tour - With Lots of DIY Ideas (blow up kiddie pool w/ pit balls)