I use quart size yogurt containers. I eat a lot of plain yogurt and cannot recycle them, so they get used to store stock. I also have some generic tupperware stuff I got at Target that I use for smaller sizes (cup, 2 cup), so I have a variety of sizes of stock available to me.

My 92 year old mother got me using half-gallon containers emptied of soy milk. orange juice, cow's milk, for our homemade broths... Still perhaps not the best solution, but free and they work well for one use. Haven't tried re-reusing them.

For smaller amounts of liquid I too use empty quart yogurt containers, and commercial ZipLock, Rubbermaid and Glad plastic storage containers with lids.

We use squishy bowls, these silicone bowls, to freeze our stock. Then we pop it out of the bowls and store in ziploc bags. The bowls are measured so it's easy to pull out exactly the amount of stock needed. http://www.bayinghound.com/Squishy-Bowl-Set-p71.html

Ditto the quart size yogurt containers in our house. We'll use them once or twice in the freezer, then recycle them. I've also used glass Ball jars, leaving some room at the top for expansion, and using the plastic lids as opposed to the 2-piece metal lids.

@racheltb - Love the silicon bowl idea! I have a silicone muffin pan (6 cups) that would be great for portioning out stock. I'm going to try that, and maybe graduate to those bowls! :)

I like the Ziploc Twist and lock containers for storing my chicken stock in the freezer. The screw-top lids stay locked down tight, so I don't spill stock all over the place when I'm trying to get them into the back of the freezer.
(Not that I've done that recently with the non-twist lock gladware containers I use...)

I reuse the quart containers from the bulk section at Whole Foods. The smaller size works well, too, for smaller amounts of broth that I use for sauteing or making grains. When it comes time to use, I run gently warm water over the bottom of the container to loosen the frozen stock and then heat it up in a sauce pan. The only caution is using water that is too hot will warp the container. Otherwise, they are very reusable!

I use my muffin tins. I have all different sizes so I put them in the size that matches my needs.

I use glass canning jars. Pour into the jar, let cool on the counter, place in fridge until cold, then transfer to the freezer (w/ the lid off!). The next day, add the lid and date.

You can't microwave these to defrost, so it takes some planning to get it ready to use.

Breastmilk storage bags! We had loads lying around after having a baby. They're compact and space saving and hold 8 ounce portions. Plus they're designed for freezing liquids, so no leaks!

I put mine in ice cube trays and then pop them out into either a larger tupperware or a zip top bag. Since an ice cube is about 2 tablespoons, 1/8 cup, it's easy for me to measure out what I need while they're still frozen and just toss them in the pot to defrost.

Just don't forget to put them into a sealed container or they'll sublimate and get weird on top.

I use canning jars with plastic lids or zip-top bags. Nothing too exciting but I guess it works well enough for me. I keep thinking that someday someone will come up with the perfect storage vessel that is square or flat so it will fit into my freezer a little bit better!

If you have a GFS in the area, I still recommend the 8, 16, and 32 oz deli containers. They just can't be beat: you can fill them, seal them, and stack them in the freezer. When you're ready to re-heat, you can nuke them a little, slide the contents into a pot/saucepan, and finish heating the rest of the way through.

I use 'bonne maman' jam jars.

Ball makes plastic freezer jars that are BPA free!

I use zip lock freezer bags. I stack them in a large roasting pan until they're frozen, in case they leak, then stack them on the freezer shelf. The advantage I think is that they thaw quickly, because they're basically flat. I don't put them in the microwave, but in a 9 x 13 pan of water to thaw.

ice cube trays. freeze. pop out. store in bags. thaw only what you need.

Ball creates "jars" for freezing. You can find them with the other canning supplies. There are also freezer worthy square containers that are usually found in the same area. I've used both with great success. I'm a little iffy on glass jars...I've broken a few with impatience.

Okay so we all know not to heat things in plastic, but what about freezing food in plastic? Is there any leaching or other bad stuff that can happen? And I'm not just talking about BPA, plastic is made up of a lot of other bad chemicals, and the stuff being used to replace BPA in new plastics is bad if not worse.

We use ceramic ramekins or glass bowls with plastic lids. They stack nicely in the freezer or fridge and nest when they're not in use. They can be used in the oven, too and are dishwasher and microwave safe (though I don't use the lids in either).

I use the Ball freezer jars as well - they come in 1, 2 and 3 cup sizes. They also stack really well! They're BPA-free, but not microwaveable.

Glass mason jars - they make a specific type for freezing with straight sides, not the gentle taper toward the top, but the tapered ones work just as well, as long as you don't fill too far, to leave room for ice expansion.

I order deli containers in pint and quart sizes from

http://www.cateringsupplies.com/modules/cart/products.php/nav_id/12/page/1/id/91/name/TAKEOUTDeliContainers

Super cheap. And I label them with dry erase markers (the writing wipes off easily with a dry paper towel) so I can reuse the containers for as long as they last.

I have a modified version of the deli container/ziplock method - I place a zip top bag INSIDE a container so it's easy to fill (I have a quart-ish sized SQUARE container I typically use), close the bag & freeze the entire thing. Then, I can pop out the bag once everything is frozen and it's square & easy to stack in the freezer. (I place them on a tray so they stay level while freezing)

Super simple, only takes up 2 or 3 containers at a time because you're just using them for the freezing process. Once they're hard, you just have a stackable frozen mass in a bag. Not sexy, but it works really well. You could use a round container, but the square shapes stack better.

I freeze stock in three different size portions. I use ice-cube trays to make 2 tbsp cubes, and then pop them out into ziplock bags. I freeze 4 cup portions in quart size yogurt containers for times when I need more stock, and I also measure out 1 cup portions, freeze them in the yogurt containers, and then pop them out and store them in gallon size ziplock bags. I like having different amounts available, and I have enough freezer space to do it this way.

I had no idea you could use Ball canning jars; great ideas everyone.

I use these:

http://store.cassandraskitchen.com/clearplasticcontainers.aspx

I'm on the ice cube team! I never, ever, ever remember to defrost my big tupperware containers of stock, but ice cubes melt so quickly that I don't have to. Plus, it's a lot easier for me to add just a little bit, so the stock gets used in a lot more recipes than just soups and sauces.

I love those new Ball plastic jars, and I was even able to find them in my small town. Previous to that, I have also used empty peanut butter jars, well-washed, of course.

I often use ice cube trays too. To make it work for lots of stock, I strain it and then simmer it down to a concentrate. The only trick is to write how concentrated it is on the bag so you add enough water to the final recipe :)

I actually also freeze a lot of liquids in regular glass canning jars. I break about one per year, usually by banging it inside of the freezer, which doesn't seem too crazy, given the number of times that I handle glass containers.

I have these trays called FoodCubers. They're like ice cube trays, except they're measured in 1/2-cup, 1-cup, or 2-cup cubes, and each tray has a sealable lid. Once they're frozen I pop them out and store the measured cubes in a ziploc storage bag -- it makes things oh-so-easy if I'm making a recipe that calls for 1/2 cup of stock. I can't find the FoodCubers online, so I'm not sure if they still make them.

I use freezer bags. I lay them flat (after filling using the deli container/bag method) on a baking sheet in the freezer. Once frozen it is stored upright in a plastic box like a filing cabinet for my soups.

If you buy prepared foods in the deli section of a grocery store - ask for a bigger container or for them to throw in an extra! I freeze stock in pint, quart and ice cube amounts.

Ice cube trays.

Also, I use the smaller corningware containers with lids (Like these)

I use freezer jam jars. I usually need about a cup of stock at a time, which is about what the jars come out to be. Also, I use ice cube trays. Freeze the stock in the trays, then pop them out and store in one big freezer bag. No leaky mess, and it's easy to use a little or a lot.

I'm on the Ice Cube Tray team- but make sure to separate your ice trays from your stock trays!

I also second the notion that this gets stock into a lot more places than it would if a large container were used. (Like savory oatmeals, rice and couscous)

I reuse glass spaghetti sauce, salsa, and jam jars. I don't usually go to the trouble of putting them in the fridge first or the freezer without the lids or anything like that. Just don't fill them all the way to the top. I leave a couple inches for expansion. I usually fill 3-4 of them per batch of stock. They fit well on the top shelf of the freezer. When I want to use it, I just take off the lids and microwave it to defrost it.

I use 16 oz cottage cheese containers or sour cream containers, they stack well, and can hold about 2 cups of stock which is a good start for small dishes. I make big soups to clean out the freezer when I have no more room for stock and other goodies.

I'm a fan of the Ziplock twist-top containers, though I have been known to use a ziplock freezer bag as well :)

While I have used ball jars for freezing before, I'd recommend it against it, especially if you have a small freezer. Shattered glass when it falls out onto your foot is not a good thing. We've accumulated a lot of various yogurt, sour cream, deli containers, and the various small sizes are easy to use and easy to fit in a small freezer.

Over here in the UK we buy 'pour and store' ziplock bags which are much tougher than regular freezer bags and have a base so they stand up on their own. We freeze all foods like curry/bolognaise/stew/chilie in them as well as soup and stock. They don't stack too well though due to their wedge shape, that's their only problem - plus we learnt that microwaving things in them causes them to become non-reusable as they get stained and so on so now we just thaw naturally or pop-out the contents and put into a bowl before microwaving.