Put them in (and out) of a muffin tin. BabyCakes is really into organization, and fitting things into place. I'll give her a muffin tin with a ball in each hole and she'll independently play taking the balls in and out of the tin. Right now I'm working on getting her to put them in organized by color.
Play catch. We roll balls back and forth. She also plays catch with herself, throwing the ball, chasing after it, then throwing it again.
Make a DIY baby ball pit. I shared before our method of creating an easy DIY baby ball pit (if you missed it read here). Four months later she still enjoys playing in the ball pit. Because the container has a lid, it's also very easy to close it up and tuck it away when she isn't playing.
The only "downside" of ball play is that BabyCakes can't quite clean them up by herself yet, so that's my job after bedtime lol. But I'll happily trade ball collection for some free moments during the day while she entertains herself.
What are you doing to entertain your toddler?