Erica came up with an easy way to create a miniature version of the ball pits one finds in those horrendous, overstimulating indoor playgrounds:
Don't throw a perfectly good baby bath away once it is used (usually for only a couple of months), buy a bag of balls and turn it into a home-made ball pool. Have you seen how expensive the ball pools are? I saved about £25 I reckon.
[The ball pool pictured here is about $50 on Amazon (there was a fancier one listed for over $250!), whereas a set of 100 play balls costs about $20. Looks like you could do the same with inflatable baby pools, which are likely on clearance right now. — Ed.]