Blogging Baby writer Stefania Butler calls Snack-Traps "essential." Little cups with soft, perforated, reach-through tops that let fingers in, but don’t let unescorted Cheerios out. Can also be used as sippy cups if you purchase the screw-on sip lids. Great for keeping the house and car marginally tidier.
Dana at Mombian adds this:
Buy at least two at a time, so if you’re in the car and your child drops one, you have another to hand back. (Having two can also help during playdates, in case sharing is required.) Snack Traps can be ordered from their Web site, although it’s not the epitome of slick design, but they’re also available at most of the major baby megastores. The company was apparently founded by a mom who developed the product for her own kids. (Wouldn’t we all like to be this inventive?)