This actually started out as a comment on OffBeat Home's 7 ways to eat healthier food on a budget.
There we were discussing make-ahead soups, freezing & reheating for work lunches. Someone asked how you'd freeze them, in individual containers or larger ones. This is my response:
While certainly not private, that's a surprisingly personal question. How you choose to do it will have a lot to do with your budget, values, and routines.
For space and best quality as far as freezer-burn goes, the best bet is going to be ziplock bags. Get the good kind with a double lock (NOT the ones with the zip-tabs), fill with the amount of *cooled* soup you want (one serving, two, four, whatever) up to about 3/4 of the bag while it's sitting on its bottom, and zip, getting as much air out as possible. Lay in a stack in the freezer and it takes up the least amount of space. However, this means thawing in the fridge overnight before transferring to a dish for transporting & reheating. If you're reheating at home, you can just drop the bag into a pan of simmering water or peel the bag off & reheat with some water (which is great if you freeze the soups rather thick, as it takes up less space). And honestly I've also reheated them by putting the de-bagged frozen brick in the crackpot and coming back a couple hours later to hot soup.
If you have a microwave at school/work you can freeze & take it in "tupperware." Where tupperware is defined as anything plastic from dollar store SureFresh to actual, you know, Tupperware. It can replace an ice pack that way which is nice, also you don't have to plan ahead as much--just wake up and say, I feel like THIS soup today (great for eaters with chronic illness who have tummy issues or food triggers). You have to leave a gap for expansion during freezing and again during microwaving, and that gap means the food can freezer burn faster--so it's not a great storage solution, long-term, but for 3 months or so you're probably alright. Again, you can thaw overnight if you wish but if your container isn't entirely liquid-sealed, you might want it to be frozen during your commute. To reheat, (and this works if you have individual containers of soup in glass, too) I recommend using half-power or the defrost option until it's thawed, then the full power for a minute, stir, and repeat until hot. Make sure you reheat thoroughly; if you have potato chunks, or meat chunks, your best bet is to reheat at full power for a minute, let sit for a minute, heat for a minute, rest for a minute, then stir and check for how much longer you might need. When done, let sit for a couple minutes and check the temp again before you down the whole thing. That method lets the heat penetrate the chunks and thus cools the broth back down as the heat equalizes. Make sure you get it nice and piping hot, so you don't give yourself food poisoning!
However, those are plastic and some people don't like microwaving or using plastic at all. In which case, metal or glass are pretty much your options. They take up more space, the metal isn't reheatable from frozen in the microwave, and the glass shouldn't be put into a hot oven. If you're using those, you're probably doing them at home. In which case, you can put the cold brick of soup or casserole even into a COLD oven, heat it to 250 for 20 minutes, then turn up to 375 and cook until the food is hot. This keeps metal from warping and glass from shattering. Of course you can also remove from their containers by running hot water over the outside and putting in a crockpot, at least for things like soup.