Souper Cubes are the unsung hero of my kitchen. They're essentially giant ice cube-like trays where you can store individual food portions. Instead of having a giant container of my leftovers tucked away in a big Ziploc or glass container, I use them to pre-portion sauces and soups into specific serving sizes. (I use the half-cup or one-cup sizes). That way, I can pop them out of their mold one at a time when I'm ready to use them.
Because the silicone is so bendy and flexible, it's really easy to release a single portion of whatever frozen item I have on hand and I don't have to defrost the entire package to do so, either.
I also get a lot of use out of the cookie dough tray — I store cut-up frozen bananas in it so that I can easily access a single piece here and there for a quick snack.