I would not keep any animal fat unrefrigerated if I were going to cook with it. Yes, I know that ghee (Indian super-clarified butter) is kept out, but this is one of my few concessions to sanitation. ;)
My mother did not save fats, that I can remember (she was pretty much the same generation as skilletlicker's, and also went through the Depression and WWII). So I guess that trait skipped a generation ;) because I do!
I have kept various fats in jars in my fridge for as long as a couple of years. Either I use it up, or I accidentally contaminate it with a dirty spoon :cry: and it gets moldy. If I haven't cooked all the water out, it can also get a bit of mildew -- but now I know and make sure there is noting but pure fat. I don't see any need to keep rendered fat in the freezer; but that is where I collect raw chicken fat until I have enough to render. If you do keep it in the freezer, make sure it is wrapped really well, because it can easily pick up off-flavors or get freezer burn.
What do I use the fats for? Just about any sauteing and browning! Usually I'll combine animal fat with a little oil, to raise the smoke point. I think it adds more flavor, especially to stews and braised dishes -- and since I defat the finished dish anyway, it doesn't really add any extra fat. (Paula Wolfert has a technique for this she calls "double defatting.") I've seen old recipes for using chicken fat in pie crust (perfect for a pot pie!) and I'll bet you could use it in biscuits, too. :lips: And I have this peculiar preference for using beef fat to make the bechamel when I make moussaka (even though I use lamb for the meat). But it's rare that I actually use the animal fats for a roux or anything we'll eventually eat; just for cooking, mostly.
One other use: if I were to make chicken sausage (expecially using white meat), I'd probably mix in some fat for flavor and texture. I did this recently with beef that I ground -- it was top round, super lean, and would have been dry as dust without extra fat.
Potatoes: mmmmm, cubed potatoes crisped in duck or chicken fat. Yummmm.
Finally: if you blanch and shock vegetables, you can use the fat to reheat them. Just a little bit gives a nice look and extra flavor.