I love mason and canning jars. They're versatile but classically pretty at the same time. I've started picking them up whenever I see them at yard sales. My sweetie presented me with two green-tinted jars on Valentine's Day - one filled with flowers, the other with candy. He did good.
Today, I'm enjoying a green-tinted mason jar filled with daffodils on my desk. At my summer solstice barbeque last summer, I filled them with sand (leftover from the patio project ) and candles. I wound the rims with copper wire and hung them from my patio umbrella and fence as lanterns. (You can see photos of both of these applications below.)
The winter before that, I filled some with salt (the kind you melt your sidewalks with) and candles and had them lining my sidewalk, kind of like luminarias. The salt made them sparkle, and several people who came to my house-warming party said they liked them.
In my house, you can also find mason jars holding kitchen utensils, safety pins, clothespins, ink pens and seashells. One also held corks until I used mine up making a wreath . I grew up watching my dad put his spare change into one of those large canning jars with the glass lid in our kitchen. That money helped pay for my college education. I put my own change in a similar jar now, but I'll admit, most of it pays for coffee and hot chocolate in The News-Gazette's break room.
And a quick search shows there are so many more things you can do with mason jars. I love this jar chandelier  and soap dispenser  (in fact, why haven't I made the dispenser yet?). You can use a jar for a terrarium and I can't wait to light my next party using this over-the-top combination of all kinds and shapes of jars filled with candles. 
Any other mason jar lovers out there? What do you use them for?