I've found just putting them in the dishwasher a great way of removing the labels but if you don't have one (I only got ours as best beloved was getting dishpan hands!) Lakeland have something for removing sticky residue from things I just don't remember the exact name for it, they do have a website which might help you.
I know just what you mean, they seem to use very sticky glue these days!
I just googled sticky label remover and several products came up, so it may pay off if you order online
headwreck - my uncle used to save all his jam jars etc and give them to a local woman who made homemade jam etc - in return she gave him a jar or two of the finished jam.
you could offer them on freecycle, or even place an ad in the local free paper, offering to save them regularly in exchange for a jar of the jam.