It's time to replace my dwindling collection of food containers. I usually buy those Ziploc/Glad disposable resuables, but they're not lasting long enough for my tastes and I'm tired of cleaning up the mess from cracked containers. Time for something sturdier!

So far, my criteria are:

Leakproof! Screw-tops would be nice for soups, fruit, etc.
Microwave-safe
Not fragile- DH and I both commute by bike some days, and we both work outside some days. We need durable stuff.
Easily stackable- I have a small kitchen with only one drawer devoted to food containers.

We pack lunches most days, so I'm looking for an assortment of 1 cup - 3 cup sizes that lend themselves well to leftovers, sandwiches, etc. I only occasionally have huge amounts of food to pack away. Right now, cost is only a minor consideration- I don't mind paying for something really good.

What do you use and like? Thanks in advance!