I like the Ziploc round containers with the screw on tops. They come in a 2 cup and and 4 cup size. Rubbermaid just came out with a 1 cup screw top container that would be perfect for your freezer jam. Ball also makes containers for freezer jam.
Diane

The Ball book has several recipes for frozen jams and jellies and supposedly you can use the small canning jars in the freezer but I have never had any luck with that. Plastic works better for me and there are several brands of small, plastic freezer containers available at Walmart. Some with snap on lids and some with screw on lids.

Dave

I like square freezer containers because they conserve space. Many of the hardware stores with canning sections sell a line of white plastic freezer containers ranging in size up to a quart. They're inexpensive, hold up well over years of use and are stackable.

Carol

I use glass canning jars of all sizes for my freezer jams... have been doing so for 40 years. Just remember to leave the lid loose until frozen... for expansion, then screw then lids down tight. I also freeze soups and sauces in glass jars. I have a "thing" about plastics... always have had.... and may now be being proved correct.

I use a FoodSaver for other things.... I know.... plastic. But it sure does help meats, etc. last longer.

I much perfer to use Food Saver bags for freezing things like meats. For liquids, I just reuse Cool Whip containers and the big margerine tubs. If its veggies like peas, corn, or beans, I use zipper freezer bags.