Vintage Postcards
Postcards were once quite commonplace, especially in times before telecommunication. Lots of vintage postcards are quite valuable today, especially Christmas postcards. While single postcards can be worth between $10-$50, ones that are signed by famous figures could earn a lot more. A Christmas card signed by Prince Charles and Princess Diana sold at an auction for $4400.
Cereal Boxes
This might seem odd, but a lot of old cereal boxes are quite valuable nowadays. Unopened boxes kept in good condition can go for up to $1000. A box of Nabisco Shredded Wheat from 1960 is worth $1000, and weirdly enough a box of Kellogg’s Sugar Pops from 2009 is worth $1600.