I've always been a huge fan of mason jars, not for canning but for decorating! The jars are charming and are fun to use.  Here is a list of creative ways to use them.

Vases:  I love to fill them with flowers and place them all over my house.  You can also wrap them with crepe paper or a doily before placing the flowers in them.

Luminaries:  Especially with Halloween coming up...putting sand and a tealight inside them (keep the cover off) to light the path up to your house.  You can also hang them from your trees with a tealight in them 

Storage:  Use them to organize a linen closet..to put q-tips, razors, toothbrushes, cottonballs.  Or in the garage...put nails, screws, tools.  Kitchen:  nutmeg, cinnamon, vanilla

Gifts:  A great way to give a themed gift..such as a gardener's gift,where you would put a package of seeds, gardening gloves, gardening tools, plant fertilizer (spikes), markers, etc..

Gifts in a jar:  pretzels, hot chocolate, beads, potpourri, nuts, almond bark, snack mix, baking mixes bath beads, foot soaks