I'll bet you'll have several people thanking their lucky stars they read this piece. It's really cool you've given people a way to not have to stand in line for wrapping paper today. Merry Christmas!

I have sometimes saved nice boxes (e.g. shoe boxes) and painted them with craft acrylics for wrapping--and to scratch a craft itch. This is also something kids could do if you have some appropriate paints and a little lead time to let things dry. Cover anything you don't want to show and let dry. Then it is easy to go back over with dots, drips, curlicues, wreaths, flowers, etc.

I bought the green bags, that they can reuse for shopping, and put them in there. And when I saw someone else also got the idea, and did it too, that was great. There are the kinds that you can fold down, and that has a snap, like a little purse, that you can carry with you in anything.

You can also tear out pretty or arty ads from old magazines and use them as wrapping paper. Full-page photos from old National Geographics are especially colorful and make your wrapped gift look like a work of art.

When I was growing up, Santa didn't wrap presents. On Christmas Eve we unwrapped the presents from family. Then on Christmas morning we ran to see our presents piled under the tree, sans wrapping. My parents started doing this when we were tiny, so we didn't question that Santa's gifts were unwrapped--that's just the way it was. Starting this tradition could save households with young kids half their gift wrap.

Another tradition is the 'dummy present'. When the gift is large or bulky, we put a tiny prewrapped gift box under the tree. Inside is a note that says to go look in the hall closet, under your sister's bed, etc. The large, unwrapped gift is waiting in the hiding place. You can re-use the gift box jewelry or gift cards come in for this one.

To expand on your grandmother's idea, you can make extra-large fabric 'Santa sacks', one for each person. All their gifts go in one giant bag, reused each year. They can be reopened over and over.

I've also had good luck with reusing Mylar balloons. I used some gold star-shaped ones to wrap books. Just cut off the seal around three point of the star, put in the book, and gather up the cut points, tie with a ribbon. I used a champagne bottle-shaped one, cut into sheets, to wrap a larger box. You can pull leftover strips of the Mylar really carefully through scissors just like curly ribbon, and use the leftovers to make a bow.
(Old VCR tapes can be taken apart for the ribbon inside them--it curls like curly ribbon, too.)

I got this idea from a geography textbook my college wouldn't buy back--use pretty pages from an old or damaged book. I use maps for graduations or milestone birthdays (particularly apt if you're giving a copy of Dr. Seuss' "Oh, the Places You'll Go), sheet music for CDs. You can use poetry or plain text for anything, and it can be dressed up with paint or drawings.

For bigger gifts, use old roadmaps, navigation charts, or the maps that come in National Geographic. My local thrift store sells the latter for a nickel, so you can stock up for those last-minute gifts. You can get maps of the places you are staying on vacation to wrap your souvenirs in.

Lastly, I keep plain wrapping paper on hand. Kraft paper can be rustic, classy, modern, or cute depending on the bows or decorations. One roll of red and one of blue has gotten me through birthdays, anniversaries, and the holidays. As to weddings, I'm still reusing the giftbags I got at my wedding three years ago. :)