It's very decent of you gxray to be considering the idea of finding another use for these jars. I used to collect early preserve jars years ago. The round ones are typically older then the square sided ones. Mason usually dated his on the bottom and often on the glass sealer lid as well. If the metal lids and the glass sealer are in good shape, it would be a shame to see them go to a land fill.
If I were you, I'd collect as many of the most complete ones and the ones in the best condition. Then maybe rent a space and a folding table at a local Sunday Flea Market for $50 bucks and sell each for $5 - $10 a piece. These look nice as a vase to hold flowers on a table, holding buttons, coins, nails, screws or just about anything else that you need storage for.
I just think that these jars are a part of our past, they're still functional and we certainly can find other creative uses for them. I believe in the motto Reduse, Reuse and Recycle.
Good luck gxray and let us all know what you decide to do.
Dave