In my ever-growing harem of Tupperware, these squeezable, heatproof silicone prep bowls hold a special place in my heart. The insides of the bowls have markings for ½ cup and 1-cup measurements, so all I have to do is toss my mise-en-place into the bowls and measure to the correct line. I also use them to pre-portion out oatmeal I make for my weekly breakfasts. On top of all that, they're dishwasher-safe, smell-resistant, and stackable: everything I have ever wanted in a kitchen storage product.
iSi Basics Flex-it 1-Cup Prep Bowls, $20.00 at Amazon.com