A few suggestions on how to reuse cardboard, even if it is recyclable in your area.
1. Reuse the boxes as containers around the house. You can decorate them with whatever you want to; paper, paint, rocks, sea shells, etc., whatever you think'll make it pretty. This sounds a little primitive, but I've discovered it to be quite a valuable asset.
2. Save your boxes and use them as gift boxes for birthdays or holidays.
3. Construct simple bird feeders. I've always had the problem of wanting a million bird feeders, but they're too expensive on my salary.
4. Arts and crafts! Cardboard can be used as backing, posterboard, dollhouse stuff, stencils, cut-outs, etc.