The most useful sizes and uses:
Jelly Jars - Great for storing pennies, pencils, extra screws, paint water etc. I find they work better for non-food items.
Olivio, Cream Cheese and other short round containers - Great for lunches, car snacks and toddler learning toys. Put in & take out!
Spray Bottles - after thoroughly cleaned can be repurposed - i have one filled with vinegar and water which is my go-to cleaner, also nice to just fill with water to keep the plants watered.
Yogurt, Ricotta and other tall round containers - make nice leftover containers, soup, if they are large enough you can poke 5 holes in the bottom and toss bath toys in them to drain. I have one in my fridge with holes poked in the lid and baking soda inside to absorb smells.
When I go on a day/weekend trip I buy Gerber Toddler meals (the ones you zap in the microwave for 30 secs) and bring them along. I normally get them only when they are on sale ($1.25) but it's alot cheaper than eating out or buying a kids meal. I save the blue containers for regular baby meals. The tray in microwavable and fits into a sandwich bag nicely! Bear also likes to play with them. I just like that they each have a meal compartment and a smaller veggie one. This morning I put yogurt in one side and scrambled eggs in the other. Bear tends to throw regular plates but doesn't throw these.
Single serving yogurt or pudding packs - I use these as snack cups at home. I fill it with cheerios or cheesy bunnies and it is just the right size for bear to walk around with!