what you said, plus risotto-- a great way that's not soup to use up stock!

you can use it when you boil pasta. It gives it a creamy/greasy feel. It's a great way to make tasty summer pasta using stock.

share the wealth with some friends!

Make a balsamic reduction with stock that reduces down forever--you'll lose a lot of that volume quickly, but end up with a rich, dense sauce for meat and polenta!

Where do you live? I'll take some!

If you know someone with a pressure canner, you can safely can it for use in the winter!

See if you know someone with a pressure canner. You can process that stock into shelf stable jars easily with one.

As well as using for risotto or pasta, you can use it to cook rice!

Instead of using it all up, you could condense it quite dramatically by reducing it to a demi-glace: reduce it over gentle heat (steaming but not boiling) until it is quite thick and let cool until just warm; pour it off into a fridge- or freezer-safe container. When completely cool, it will be a soft-solid consistency, something you could pick up in your hands.

A puck of demi-glace will keep well-wrapped in your freezer indefinitely, but in the years before refrigeration, the stuff was considered to be, essentially, shelf-stable. More recently, chefs would keep a puck of demi-glace in the fridge and simply pick off any mold that developed. (N.B.: I am not suggesting you keep it at room temp or store it long-term in the fridge, just that in other times it was considered safe to do so.)

It's handy to have around: because the liquid content is minimal, demi-glace is great for flavoring dishes, especially sauces, without watering them down. A little goes a long way and, of course, it's so very reduced in volume that it takes up very little freezer space.

I would make some of Ina's gravy to portion out and freeze for quick meals throughout the fall. This is the most amazing gravy I have tasted, even without the pan drippings. If not adding drippings, go with that extra tablespoon of cognac, sherry, or marsala :)

http://www.foodnetwork.com/recipes/ina-garten/homemade-gravy-recipe/index.html

Does the person you got the stock from have freezer space - maybe he/she would store some of it for you until you've used the first lot?

I use it in place of water in my savory pie crust, so you could make up some crusts to freeze or use now. Not that you need 6 quarts worth for pie dough, but you could do a bunch of dough to keep on hand, since a round of dough takes up much less space than a quart of stock in the freezer. You could also use it to steam vegetables for extra flavor, poach some chicken, use it for cooking down some greens (I always use stock instead of water when making kale or collards), or use it as the base of a brine for roasting some chicken to have on hand for quick meals during the week. I also like the idea of freezing stock in ice cube trays and then popping the cubes into a bag to keep on hand to drop into sauces for a little added depth of flavor. I can store a freezer gallon size bag of cubes on the door of my freezer, so it doesn't eat up too much freezer space. You could break it down into quart or even sandwich sized bags so you could fit it in the freezer around things. You could also make a hot soup that can be served cold. I make carrot soup (stock, onions, celery, garlic, salt, pepper, fresh thyme and dill, tons of carrots, cook down and puree with immersion blender) that we serve cold in the warmer months and it is even better than hot!

Risotto and roux-thickened mushroom sauce with pasta are both fantastic ideas. We also cook Asian-style flat wide wheat noodles in broth - the flour thickens the broth and, tossed with chicken and scallions, it becomes a delicious meal. Any kind of noodle is delicious cooked in stock, really. I also eat ramen noodles cooked in broth with an egg stirred in for breakfast.

I personally rely heavily on condensed stock to save space; reducing it yourself is a great idea so you can still have the delicious stock later!

I'd use it to cook lentils, it will give them awesome flavor. Cooked lentils can keep for a week and can be used in so many different ways (lentil burgers, lentil loaf, soup, etc.). Good luck!

Too hot for soup? Nonsense! Use it in a gazpacho!

I came here to suggest reducing it down to a demi-glace as well. You should end up with a dense dark jelly that will take up very little room. Then you can add a tsp to a stir fry or pasta sauce with no problem. Feel like making a soup after all? No problem, just add water plus your demi where you'd add stock. And this keeps for a really long time in the freezer.

use it to deglaze pans with a click of butter and make beautiful sauces.

Use it to make rice, and use some every time you sautee veggies or meats. Its a great flavour for EVERYTHING!

Stock is great for cooking ANY grains -- not just rice or pasta. (Wheat berries, barley, amaranth, couscous, quinoa......) Many of these grains absorb quite a lot of liquid as they cook, so you'll probably use up a lot of the stock if you use it this way.

The Kitchn has featured myriad grain salad recipes this summer and in previous years, so i suspect you'll find something that pleases your summer palate. :)

What a generous gift!

Make a big pot of soup and take it to a soup kitchen or hand it out to people on the streets.