Does anyone know if it's possible to can cooked meatballs in sauce in the same way that it is possible to can fruit, or pickles? Or, is freezing them, in sauce, in some kind of an airtight plastic bag best? Any advice would be much appreciated.
When ever you can meat, it must be done in a pressure canner in order to be safely eaten. National Center for Food Preservation has a lot of good information on that http://nchfp.uga.edu/. To make meatballs, you would pre-cook until rare and then the pressure canning would finish the job. In my mind the best taste and the easiest would be frozen in sauce.
Let me second the "freeze" is best (and easiest) option. Yes, you can can (hmm.. not the dance) if you use pressure canning, but you must also use an approved recipe (see the site that SKK recommends) and follow it to the letter. If you have your own recipe that you really like, freezing will be your best preservation option.
I think freezing makes for a better option than canning meats if possible. Another option is to make it into jerky (aka dried meat). I have had great success with turkey, venison, and beef jerky. I do have a dehydrator which makes it easier. You can also use them to make dried fruit and leathers , dried tomatoes, and herbs.