Use a hula hoop to simplify ball-catching games with young kids
Kirsten's ball-playing hack would work well indoors, too. (I'm thinking rainy day basement play.)
You know when you're playing catch, soccer, baseball or such games with preschoolers or toddlers? They always move really close to you in between turns, and you have to keep moving them back so there is room to throw/kick, etc. I started putting a hula hoop on the ground where they should be, and they stay in the hoop (or if they don't, it's 'Quick, back to the circle!') and you get more time for actual playing. I think it's less confusing for the kids, too.
We use hula hoops to play big indoor hopscotch, too.